Martial Arts feat isn't applying to all text, and displays incorrect modifier and value in some places (marked in red).

Lv 3 Tabaxi Monk, with STR 7 (-2 mod) and DEX 18 (+4 mod).

Actions panel text:

On mousing over the -2, the alt text states "modifier:str".

Side panel text (after clicking the Claws action):

Stat block at the top shows the values correctly, and the damage roll button correctly uses DEX modifier, but flavour text in both places indicates it'd still be using STR mod instead and shows the wrong modifier value.

Not an error.

The Martial Arts feature cannot, and should not, override the text of other features. That includes the snippet codes. This is to reference what the feature properly is. The action on the sheet takes into account the Martial Arts feature for you as a convenience.

Quote from Cyb3rM1nd >>

The Martial Arts feature cannot, and should not, override the text of other features.

Ok... why?

The character sheet should be clear and unambiguous when playing, otherwise what's the point in having one when you could just refer to the PHB for everything anyway, except for maintaining a flat list of your XP, Ability Scores, and other character selections. If this isn't an 'error' then it's an insufficiently clarified UX feature, as it shouldn't directly contradict itself (which, taking the character sheet as a self-contained unit, it does unless you go digging to find out why it does so).

Quote from Cyb3rM1nd >>

This is to reference what the feature properly is. 

If I wanted to know what the feature "properly is" in general cases, I'd refer to the text in the PHB/sourcebook. If I wanted to know how it operates "with respect to this character", I'd use the character sheet. That's the purpose of a character sheet vs the purpose of the PHB.

Quote from Cyb3rM1nd >>

The action on the sheet takes into account the Martial Arts feature for you as a convenience.

Problem is, in one location the action does take into account the MA feature, in another (barely an inch lower down on the same page) it doesn't... and surely the whole point of the entire character sheet is to summarise everything about the character, "as a convenience"? Looking at the sheet, I can see (under "Actions -> All" or "Action -> Actions" ) an entry in a table called "Claws", with a clickable die roller with text saying "1d4+4"... then immediately below that an entry describing "Claws" with text saying "... that deal 1d4-2 slashing damage" - you can see how this could be confusing, right? And not at all "convenient" to have to go looking for why the two don't match? The exact opposite of convenience is reading in one place "1d4 + STR mod" and having to remember that I have MA which turns it to DEX. I'm not saying it's hard to remember, I'm saying if it's convenient to show the actual values in one place, why is it suddenly not convenient to show it less than an inch lower down also? If I just handed you a character sheet out of the blue with no preamble explaining it, and you had two descriptions of the same action showing two different rolls being made... how would you know which one were correct? By itself, you couldn't.

For that matter, were this a paper sheet and you were writing up this build yourself, would you robotically duplicate the exact text from the PHB in saying "Claws attack = 1d4 + STR mod", then further down the page write "btw, actually, that Claws entry above should actually be + DEX mod because of the other feat you took", or would you just write what is relevant for that character in the first place, knowing that you've got Martial Arts? Is the character sheet supposed to duplicate the detail in the PHB or is it supposed to be relevant to the character of which it's the sheet for? For this character, who cares that "if I didn't have Martial Arts then it'd be STR mod as the PHB says" seeing as you do have Martial Arts?

One of the major advantages of having digital character sheets is that it can do all of the calculations and the conditional display work for you, including the conditional display text. I don't think "but that's what the exact text is in the PHB for this exact item" is a good argument in this case, because the text in the PHB doesn't take into account the other feat you have which modifies this ability.

I feel that if the intention is for the character sheet to be clear then it should either only reflect the values and text that are relevant for the specific character to which it is referring to, or if you really need to be a stickler and copy the exact PHB text to the character sheet in its entirety "to show what it properly is" then the text should have a very clear line below it showing that the above information is modified by the additional feature. Or something in the mouseover text. Or something other than what there is currently to explan the seeming discrepancy... which is absolutely nothing. When you click the "Claws" entry, it's because you want to know more information about the Claws ability as it refers to this character, not as it is in isolation.

I mean, if you really want it to exactly duplicate the text in the PHB, then why couldn't you just have the text say:

The character sheet was intended to minimise the need to look up the PHB.

The way it is now gives you the feature as written in source, and the actions to reflect the changes on the character sheet. Many of us prefer it this way.

Implementing what you ask - having one feature entirely overwrite another - is a very complicated and time-consuming process that would benefit very few. I sincerely doubt they would bother. However, you're certainly free to raise it as feedback on what you'd prefer. There's a feedback forum for that. Maybe consider a poll to see how many want this.

I'm just saying it's technically not a bug. It's working as the developers specifically intended.

Ok, if that's how it's intended then I agree it's not a bug. However...

Quote from Cyb3rM1nd >>

The character sheet was intended to minimise the need to look up the PHB.

I guess this is the issue I have with how it's written right now though. Looking purely at the text for Claws in all locations on the character sheet, there's absolutely nothing which points to why the damage rolls are different in different places. It's just "here's two differing damage rolls for the same thing, now go away and look up all the different feats, racials, etc in the PHB until you find the particular one which makes one of them different and only then will you know which one is right" - exactly the thing the character sheet is supposed to minimise the need for. For those extremely familiar with classes and feats this would be child's play (to be fair in this specific case I guess if you've ever played a Monk then chances are you'd know exactly why they differ) but as I said before, for a new player this would be confusing, and frankly painful to have to pore through just to get an answer as to why their claws do supposedly two different damage rolls.

I mean, the conditional logic of modifying Claws because of MA is already built into the character sheet, proven by the fact that a) the rollable damage button shows the DEX-based value, b) the sidebar "Damage: " field has the right roll and c) "Stat: " says DEX, and considering I do understand both conditional logic and programming, I still don't see how it would be "a very complicated and time-consuming process" to add an additional line at the bottom of the sidebar text stating "This damage roll has been modified by the Class Feat Martial Arts". Just something to point the way towards why they differ, as opposed to just serving up the two options and making you cold search for the reason.

I shall do as you suggest though and put something in the feedback forum about this. I will say that anecdotal evidence from me just starting a new campaign with 4 people who have never played 5e (and me never having played but never as a Monk) does show that the way the sheet is at the moment is anything but newbie-friendly though.

Features & Traits is the straight information for everything all separated out. Actions is where things fit together that can under the current programming.