Starting info:

I noticed that when trying to toggle a comparator's modes(from subtract mode to compare mode and vise versa), that comparator may briefly turn off if powered and has a repeater facing towards it from the sides, even if the repeater isn't connected to anything. From what I can tell, the time that the comparator is spent off in this glitch isn't enough to break contraptions, but CAN be visible from the f3 debug screen, as it stops saying "true" in the "powered" info for the comparator. It was difficult to get the screenshots of this happening, due to the glitched state's window of time being really small.

Test 1:

After I closed the world and reopened it again, the glitch could still be done for about a minute or so before it stopped happening. It may be caused by some sort of lag, so it might be a good place to keep looking for some investigation.

Test 2:

Upon further Investigation I can deduce that for a short period of time after the world loads, more specifically the loading and unloading of chunks, might be the cause of this. This is because it seems to be consistently happening when I enter a world, though when I first noticed it, the world had been open for a good while, and I must of unloaded and reloaded some chunks without noticing around that time.

Observations(Tests 3+):

• It seems to be happening whenever the world has just been loaded, as well as possibly the loading of chunks.
  • Updated info: Through more testing, the glitch is NOT determined by loaded chunks.
• It most likely happens whenever a comparator is powered in any manner.
  • Updated info: Only certain power sources cause the comparators to glitch out directly.
• The comparator closest to the redstone block in the images below doesn't glitch out, but the other one does.
  • Updated info: Certain power sources cause the comparator to glitch out more easily than others.
• The comparator in the video for MC-10653 glitches out in a similar manner.
  • Updated info: The comparator in the video for MC-10653 explains this glitch in one case(Note: MC-10653 is the original post of the glitch).

Final test(Briefly mentioned in Observations):

After doing loads more testing, I realized that certain blocks cause the comparator to glitch out directly, whereas others only cause the comparator to glitch out if it is directly behind another comparator. The instances that the comparator doesn't glitch out are seen on the red wool on the left. The instances where the comparator does glitch out, but need another comparator behind it to cause it are shown on the orange wool in the middle(Note that any instances of the orange wool do not glitch out when the closest comparator is the only comparator that is being powered by the specific block.). The instances where the comparator glitches out without the need for an additional comparator are shown on green wool on the right.

Conclusion:

Redstone comparators seem to glitch out when next to certain blocks that cause it to become powered,