Yealink HDMI ingest - lag and call failure

We have many Yealink MVC800ii and MVC840 MTR systems running in our meeting rooms. We're seeing real issues with HDMI ingest, particularly using the HDMI cable that connects to the MTouch II panel, and less so when using the WPP20 wireless dongle - but both are not working optimally.

The usual pattern is that either presenting or sharing content (both scenarios are affected) works until around 50-60mins into a call/meeting then things start getting really laggy. Mouse moves or slide navigation are delayed and not seen on the front-of-room displays or by external participants for several seconds. The delay then starts to extend to 30+seconds, usually resulting in the call eventually dropping and the MTR needing to be restarted.

This is happening in different rooms, to different users using different models of laptop and when sharing content stored locally on their devices as well as opened directly from M365 services such as SharePoint or OneDrive.

All indications point towards a problem with the in-room kit, like a memory leak. All of our systems have fully up-to-date software and firmware and I've confirmed that they are restarting nightly via the 02:01 scheduled task. Other than Extron CTL100 workplace controllers installed in some of the affected rooms, there is no 3rd-party hardware involved in the MTR set-up, its all standard Yealink kit. We've swapped out components, cables, and even factory reset and rebuilt some systems.

Call activity and system health shown in the TAC rarely show any issues. Sometimes there is a report of 'poor' audio quality in some (not all) of the affected meetings, but generally everything appears 'healthy' or 'good'.

Has anyone experienced these symptoms (with Yealink or other manufacturers)? Or any ideas on what to try? It's now a real problem for us as we open more MTR equipped rooms.