When Schema:Edit logging is enabled but the user isn't in the bucket – 93.75% of users – mobile edits will succeed but the editor overlay won't close. When the user refreshes the page they'll see the "Success! You're edit was saved." toast.
This regression was introduced in 9b239fa.
I suspect that this is the cause of https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)#Edit_acts_like_it_won.27t_save.
- wmf.13 hasn't been deployed to enwiki yet and it looks as if it's already been resolved.
- This code is in wmf.12 as well.