I started with trying to create a 'new' level 5 character.  Once having done so, and trying to load the character sheet, it just came up as an infinite spinning red circle and the sheet never loaded.  Not certain whether or not this was a bug, I went on exploring other aspects of the new updates while leaving that page to load in a different tab.

After making a monster or two, checking out the campaign builder, and a few homebrew items, the page was still stuck in a spinning red circle.  At this point, I figured, it was time to test the exact source of the problem.  So, I deleted the character and went back to the builder and started the character as level 1 with all the same features and choices.  Once finished at level 1, the character sheet loaded.

Step 2, I upgraded the character's XP to 6500 (Level 5) - the sheet still loaded.

Step 3, I upgraded the class (Paladin) to level 5.  Behold, the sheet is now stuck in the infinite loading cycle again.  So it seems a bug of some sort exists at making a Dragonborn Paladin level 5 instead of level 1.  Perhaps it was the ability score adjustment at level 4, or the fighting style choice at level 2?  I don't have the time to test more specifics at this moment, but I shall try to provide better information in the future.