Issue with users being disconnected

We have a customer on AX2012 R3 (6.3.1000.309) and users are randomly kicked out of AX during the day. They can get back in but may be kicked out again. This tends to happen when they are doing something eg changing companies. This is affecting multiple users across the system. We are noticing the following Info message in Event Viewer coinciding with the user being kicked

Object Server 01: No ping from client session 12 (User: AUser, ClientType: GUI). Terminating the session.

There’s also a related issue with user’s sessions timing out when they’re away from their machines for c 45 minutes despite their user options having Automatic Shutdown set to 0.

Things we’ve done to investigate

confirm client / AOS version is insync

confirm clock/time on AD server is accurate

refresh client config file on one of the AOSs that had become corrupt

Is there anything else we can do to rectify this. It is impossible to replicate but we must be missing something.

incidentally there are quite a few entries in sysclientsessions including old values where status = inactive and lots of sessions of type ‘Worker’. Could clearing these out by part of the solution?