I cannot reply to Sync only making partial update to file so making a new post to update it for anyone who gets the same issue.
I just had the same issue. Added a line to a note on my phone, then an hour later opened my pc and went to the edited note. It did not have that new line in it. Suspecting I closed obsidian on my phone too quick after editing and that background syncing is not supported, I opened obsidian on my phone and waited a few seconds. After 3 seconds the sync went through because on my pc, the note had the new line show up. worked perfectly