Hello, I tried, no improvements, same error.
Here are more details:
1) Problem occurred for different users using different browsers (FF & Edge Chromium).
2) My FF version is 80.0.1. Problem persist when disabled hardware acceleration.
3) Mgmt host is in one subnet, NCE together with NEs in another. There is no firewall between NCE and NE. There was nothing blocked on the firewall for all connections from mgmt. to NCE.
When error popup was raised in browser, corresponded tcp session (port 31493) was closed at the same time. Traffic was captured traffic between NCE and browser (this session was built earlier with success and some amount of data was exchanged between endpoints). TLS close was initiated by NCE side.