Any time I need to change the title on my document to capitalize it on Android it always tells me that the file already exists after I click off the title.
All you have to do to reproduce it is:
Create a document
Click into the note off of the title
Go back on the title and capitalize a letter
Click go back into the note
Voila! “File already exists”
I think Obsidian itself doesn’t allow files in the same folder to differ only by capitalization, because internal links are case insensitive (tho also some file systems have the same issue). Obsidian could probably communicate more clearly about it, tho.
That Stack Overflow answer illustrates that Android needs to handle either case due to potentially connected devices and such, and so while the underlying file system can handle files which just differ in case, it’s a system choice to call these files identical.
So you need to use the workaround of renaming into something else first, before you can rename back to the same file name with a different casing.
Update: Moved post to Help since this isn’t a bug within Obsidian