@Coconut
Not a known issue, but it does appear to be a problem. It also illustrates how few people use notes on mobile too - because this appears to have been an issue since the last site update. A fix will be coming soon, no app update required. (It is fixable server side)
No quick fix for this.
A pretty unfriendly workaround is to write your notes, then make an illegal move, which will then save the notes. You can then make your legal move to continue.
A fix is forthcoming...just patching this whilst retaining backward compatibility with existing app is causing a bit of a headache.