I've recently answered to a similar thread describing this problem in 1.15.2 (showed below), but since it affects also the latest forge version I think it deserves his own post (sorry if I shouldn't have, I'm new to the forum).
Replicated in forge-1.16.1-32.0.24 (latest) with no mods installed in a new 1.16.1 minecraft world. This bug does not occour in vanilla 1.16.1
Bug description:
(I'll just quote what RescueGum wrote in the 1.15.2 post, since the bug works in the exact same way)
I add that the comparators affected by this problem update also if you right click on them, similar to how they behave when you open the doublchest as described in the quote.
Thanks for your attention, hoping this bug to be addressed soon (I've noticed it's pretty old).
Have a nice day.