For customers experiencing any issues with their NBN service, we recommend the best thing to do first is check if there's an outage on the NBN network.
We have created this article that can guide you: How to Check for NBN Network Outage
In your case, the synchronization is stable, which is an indication that there's no line fault affecting the service.
Further investigation may be required to identify what is really dropping out as it could be the Wireless connection, if you're connecting all your devices via Wi-Fi.
Wireless dropout can be eliminated by using a wired connection. If the connection will not drop on a wired device, it is likely a wireless drop outs issue and we recommend having a read of this community article which may help improve the wireless connectivity performance : Easy Steps to Improve Wi-Fi Connection In Your Home