As well as not syncing well, I'm recently finding that items just disappear from the Android app, sometimes temporarily, as I watch.
I've even seen a parent item disappear, but its children are then promoted to the main (smart list) view. Sometimes they come back minutes or hours later.

Not being able to reliably see tasks on my phone means I can't see much option but to migrate painfully to another (otherwise worse) solution if it's not fixed. 😟