@mbartosh - I think there’s a clue fairly early in the client log you posted.
RegisterOnce: Attempting secure registration with 'https://REDACTED:52311/cgi-bin/bfenterprise/clientregister.exe?RequestType=RegisterMe60&ClientVersion=10.0.1.41&Body=0&SequenceNumber=4&MinRelayVersion=22.214.171.124&CanHandleMVPings=1&Root=http://REDACTED%3a52311&AdapterInfo=00-50-56-bc-94-3c_REDACTED%2f24_REDACTED_0'
Comparing with my RegisterOnce messages after rebooting/restarting the BESClient, your URL’s parameter ‘Body=0’ should contain the BES Client ID. Also the SequenceNumber=4 is a very low sequence number, like what I’d expect with a newly-installed client.
For instance my message looks like
RegisterOnce: Attempting secure registration with 'https://REDACTED:52311/cgi-bin/bfenterprise/clientregister.exe?RequestType=RegisterMe60&ClientVersion=10.0.7.52&Body=1614594029&SequenceNumber=514&MinRelayVersion=126.96.36.199&CanHandleMVPings=1&Root=http://REDACTED%3a52311&AdapterInfo=00-15-5d-01-02-03_192.168.1.0%2f24_192.168.1.36_0&AdapterIpv6=00-15-5d-01-02-03%5efe80%3a%3ad12%3a3a9%3a860%3a3acf%2f64_0'
I’m still liking the idea that your BESClient service is sometimes starting before your Startup script restores the registry keys, which could also account for why it sometimes resets and sometimes does not (i.e. a timing issue between Machine Startup scripts executing & how long it takes for all the Services to start).
I’m going to try tampering with my client (removing the registry values, removing the client keys) to see whether I can reproduce the log symptoms at least.
Also, if you don’t mind, could you restart the client and then post the portion of the new log with the computer info on restart? My 10.0.7 client log reports the existing Computer ID before it tries to register to the Relay, while yours does not; I’m not sure whether that’s a logging change between 10.0.1 and now, or whether the computer ID wasn’t reported in your log because the computer didn’t have one yet. Restarting the client service on a working machine should give a clue there.