My ~/xsession-errors file has grown to several gigabytes size, mostly flooded with the following message:
[SOLUTION]vdpau_chroma filter error: [00007fc82c01c4e0] video mixer rendering failure: An invalid handle value was provided.vdpau_chroma filter error:
video mixer attributes failure: An invalid handle value was provided.[00007f433801c4e0]
Maybe related to
Bug #1846374 on Launchpad: "Having a video playing/paused when switched to another user generates gigabytes of error logs"?
To be continued...