DISCLAIMER:
I am uncertain if this bug has already been reported, but couldn't find anything on the browse page.

How to replicate:
Place 2 observers (an observer clock) running into a redstone lamp, being observed by an observer. The final observer will pulse despite the redstone lamp never visually changing state (nor the blockstate changing in F3).
1.20.2:

Expected Behaviour:
Final observer has no output as the redstone lamp is not changing state.

Discovered Behaviour:
Final observer pulses in sync with an identical system with the lamp replaced by a noteblock.

Potential Cause:
The lamp is turning on and off in one tick, scheduling the observer to pulse but no visual change. This result cannot be replicated if the lamp is powered or a second (misaligned) clock is also powering the lamp.