OPC-UA comms problem with Topserver

We have a curious problem that has surfaced after problem free running for several months.
Our OPC tags from topserver have started to intermittantly not update. The quality remains good but the values do not update after a while they become stale.
Topserver is running on a seperate virtual machine and different host to the ignition gateway. Both hosts are windows hyper-v server 2012 and both virtual machines are Windows server 2008 R2.
We are running topserver version 5.15 ( the latest) and ignition version 7.6.4 Tags that are from the ignition opc server are unaffected.

The problem can be overcome by re-booting the ignition machine but returns after about 36 hours and is then cyclic with about 20 minutes communication followed 40 minutes approx failed communication. Starting and stopping the topserver OPC server results in a oneoff update of the tag but thereafter comms continues to fail in the same pattern.

I cannot find any pertinent error in any log or errors that are similar in tme stamp to the start of the comms problem.

We have also noted that when comms resumes the time stamp on the data is significantly ( perhaps 20 - 30 seconds behind true time when viewed using the Ignition OPC viewer. This slowly drifts into the true time before slipping behind and comms failing again.

Ideas please


Can you add the Gateway Console logs, to this post ? Hard to say what might be happening without looking at the logs. When was the last time that this happened ?