I'm trying to make a homebrew monster stat block based off of Asteria's from the Book of Many Things. Every time I save it, it returns an Internal Server Error. The stat block still shows up in my creations as Copy_of_Asteria, but when I open it, it includes the changes to the name and that stat block that I've made. 

I tried making a homebrew monster this morning and also encountered this same error. However, I did not experience the accidental success of finding the stat block showing up in my creations. I'm not sure what's going on. Although I don't use the homebrew monster creation very often, I've used it successfully in the past. It used to just ... work.

This happened to me last night, tried again just now and it seems the problem is still up. Internal Server Error whenever I try to save changes to a monster. For Chrome in Windows 10 and Chrome for Android. The first time was like @Exington described. The second time it didnt save any changes at all.

Happens to me as well, but seems to only happen when trying to home brew certain monsters... if it has spells, seems to always come up