Could be a good lead....
Old HDD, some higher temps, some errors - all warnings. Nothing wrong ("passed") but "failed" may be too late. Get backed up ASAP.
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The errors/flickering may not necessarily correspond with the opening and closing file explorer per se. Your system is doing lots of other things as well. May take two things happening to cause the flicker.
If you have not done so look into some of the other logs available via Event Viewer....
Also take a look at the Performance Manager. Watch what happens to the HDD as you open and close file explorer and do other things. E.g., lots of faults when Word is opened. Bad sector, tries and tries, heats up.
Back up the HDD first. Verify the backup.