There is definitely noise ingress on the circuit, you can show them the logs and RS errors, and ask the tech why you are losing the SYNC time stamp. The trouble with noise ingress is that it tends to be bursty and intermittent and can be hard to pin down.
I take it you have checked your coax cable from the Hub to the cable entry point for obvious signs of damage and all connections are hand tight and there are no un-terminated splitters legs. The Tech should have done it but always worth a quick check yourself.
Engineer came round today 23OCT19 at apptoximately 1300 and worked on the external equipment where all the individual flat cables go to one wall mounted port/hub/tap. Not sure exactly which components were replaced but the engineer said everything was replaced and is now housed in a lock box instead of exposed to the environment.
After they finished I reset the hub using the reset for 90 seconds. Allowed 2 hours and took the following records from the hub:
There were no errors showing on the network log but as I was trying to get this together I got a call from the engineer asking to come back to fit an attenuator onto my hub as the signal strength was too high. He fitted a 10db one on the hub 3 port.