System unusable after update. Again. Nothing listening on port 11000?

I'm back to having 4 unusable nodes on the network due to an update. Have been through this loop a couple of times now and the only way to restore them is to do a factory reset. They show up on my network monitoring page, and I can go to the web control page for each of them (on port 80). Each one is on a wired connection and no, rebooting the router isn't the answer to the issue ,despite the number of times it's requested.

I've had numerous emails from the support team and mailed them multiple diagnostic logs, including one for the same PowerNode before and after a factory reset for comparison. No other solutions apart from rebooting the router have been offered.

I may be clutching at straws, but it seems to me that the key issue is that the Nodes have failed to start listening correctly on port 11000. This means that all the functions that issue commands on that listen port (options on web page and the android control app?)

I was wondering if anyone else has had issues with loss of control on 11000 or can suggest further things to try? Failing that is there a way of shelling onto the boxes to inspect the configs and logs  as seeing errors such as :

Nov 19 22:21:51 (none) user.emerg ./ms.pl: main::__ANON__ ./ms.pl (119) malformed JSON string, neither array, object, number, string or atom, at character offset 0 (before "\x{18a961}\x{2a5}e\x{11ad}...") at OAuth2Service.pm line 43.

in the log doesn't fill me with confidence.

Thanks