Reliability of synchronization

I’m using nextcloud since 2 mouths and sometime, I had very bad surprise because, in some case, nothing is synchronized.
I’m luck because in most case I just have to go to my applies to see “modfied version” of calendar entries/notes but i’m very stressed and I can’t thrust all i saved ?

There is no way to know really if something is synchronized, sometime, i’m sure the internet connexion is good, but no syncing, sometime, I know internet is not good but syncing is ok, but no way to know when syncing is ok or not ?

I’m use apps for android (from f-droid and googlestore), and linux, and lithenning calendar on thunderbird.

It’s boring to necessarly verify in all my terminals to control if all my rendez-vous and notes are synced …

Is there any way to solve it ?

If it doesn’t happen regularly, it’s a bit hard to debug. But if you encounter such a problem, I’d look in the server logs (nextcloud and webserver) if there is a request from the client. Perhaps the request was denied for some reason. If you can’t find anything, then it’s perhaps on the client side. The desktop client can be run with active logging. For calendar-syncing or mobile phone, honestly I don’t know …