The chain seems corrupted again the end of the debug.log says
The lines that you posted don't contain the actual issue, it's all about core's shutdown procedure.
Include a few lines above the ones you've posted.
I normally press the x in the top right corner
Hmm, so you have been shutting it down normally.
You should now consider scanning the PC for possible hardware issues.
Find a tool to test the HDD for bad sectors or faulty sAta cables or it could also be your RAM.