[kristop]

That is incredibly strange. No other user has reported anything like that happening, and I didn't really change anything related to layers in the previous few updates, so it's it seems like something unusual occurred in your database. Did this issue occur after updating MobileSheets? Or did it occur after some action like synchronizing your library? Do you use the companion application?
As a side note, not being able to reorder layers is not a bug or anything of that sort. I just don't support reordering layers at the moment. The reorder arrows are only for reordering annotations within a layer.
Thanks,
Mike

Updating MS ? I remember seeing the change list recently, so probably... I am now in 3.8.36.
Syncronizing my library, yes, and through companion, yes. I did upload several times several files recently, and edited several others to add the timings.
(Note that I have a file in my library that always creates a wifi connexion problem, I am unable to update it (just to add the time), rather big file, whole op28 Chopin 108Mo 50 pages.)
(My DB weighs 1.19GB.)
I don't have a backup, but it won't be that long to rearrange the layers, I don't have that many files with annotations, I just began experimenting this feature. (I will have a question about the possibility to import the Pdf layers as MS annotation layers... but that's another subject. I didn't even make a try yet.)
Thanks 
(Can I do something to help ? I am waiting a bit before updating to 3.8.39)
PS: About reordering layers, yes I remember now reading in the Manual that the arrows were just for the annotations (after I found that my layers had been swapped ; that was a long time ago, several months).