Hi, I've noticed the same problem, and it's extremely frustrating because Joplin is amazing in every way except that it sometimes loses some of my content, which is terrible! I rely on Joplin for many things since I'm autistic, and this is becoming a real problem for me!

I use Joplin on Linux PC and on Android, they're synced using Joplin Cloud with encryption. I've noticed it happen when using Joplin on Linux PC alone with sync (no Android). So it's not an Android issue, it's an issue with how the core sync works. Maybe related to the fact that sync works slowly which allows edits to happen during sync?