The online score is dropped when your node has offline audits in the checking window, i.e. when the satellite is come to audit your node it was not online - didn’t answer on audit request.
So, you should figure out why it could happens. I have a few thoughts:
- your router dropping packets from time to time (could be some anti-spoofing protection enabled on your router)
- you have several places where DDNS updater is running (Node shows offline periodically)
- your node overloaded for some reason (slow storage, or it has a noticeable latency)
- also worth to check - do you have started GET_AUDIT but never finished?