Not sure if this ever got solved for OP, but I’m also seeing some files being replaced with  with the Android app. It happens on some files and not others–not sure why. But it particularly seems to affect brackets, bullets, and headings. E.g.,
## Main
- Continuing
- [ ] [[Noninvertibility]]
becomes
Main
 Continuing
 Noninvertibility
Note here that Main and  Continuing were actually both preceded by U+200B “zero-width space”. This seems to only happen for bullets/headings that have sub-bullets/headings, so maybe it has something to do with the rotating fold/unfold caret.
Also, I haven’t checked them all, but I think all the  are U+FFC “object replacement character”.
I suspect this is an interaction between Samsung’s keyboard and the unicode styling elements used by the WYSIWYG “Live Preview” editor, so I’m disabling Live Preview on that device. (Options > Editor > Default editing mode > Source mode).
I also am using a non-Obsidian sync method (syncthing) on these files, but I don’t think that’s the problem (the corruption happens the moment I open the file for editing in Obsidian). The files are also on an SD card, but I don’t really think reads/writes there are a problem either (they aren’t generally a problem there, for either most Obsidian files, or for other apps).
I’ll continue to watch and see if disabling Live Preview fixes it for me, and after updates cautiously commit files to git and then try re-enabling it.
I don’t use custom themes, and that device/vault had the custom plugins “Calendar”, “Dataview”, “Excalidraw”, “Periodic Notes”, “Templater”, “File path to URI”, and “Heatmap Calendar”; and I’m now disabling the last two.