Some redstone torches(all torches on the top of the screenshot) behave strangely when it is placed in certain areas, or putting them next to each other. Torches can produce different outputs even if they have the same input(they were all controlled by the same redstone dust line).

I have uploaded the scenario that produced this strange torch behavior. (the repeater in the middle at the bottom was set to 2 ticks)

If you want to see the bug in action, I can provide a video for you.

(this bug might have appeared before 1.8.3, but i have only tested it in 1.8.3)