Spent some time just watching FT8 waterfalls, where it is obvious that some stations are off timing.
What is telling that quite a few seem to be on the same “off” together, suggesting that there may be a computer clock induced issue.
My theory is that many stations experienced the same NTP issue simultaneously moves their time sync off in-mass.
If the cumulative offset is too much, decoding stops and the operator will look for a fix, otherwise they will continue on.
There are specifications to all this, but as I mentioned upgrading my NTP service to the latest sorted out my PCs.