@Dhranios following your comment I have made a feature/change request on feedback.minecraft.net, which got silently deleted. No email, no reply saying why, not marked as anything in my requests, nothing. Clearly mojang does not consider it valid as a feature/change request.
Able to reproduce in Vanilla 1.16.1
I'll check tomorrow, guess I'll finally have to update to 1.9 or later
Most likely because the NBT range is different in 1.8
happens with /kill @e
Xfce does not appear to have this problem
Cant reproduce, however, I am using a different version of ubuntu. (Xubuntu)
the point is, in case 1 the repeater does NOT turn on, but in case 2 it Does.
ive added a screenshot
in this case, the repeater DOES turn on
the problem is the hitbox of a zombie.
the hitbox of a zombie (which can be see by pressing F3 + B) can sometimes glitch in the hitbox of a door. however, i do believe this is just a directional glitch.
when the hitbox of a zombie and something it wants to hit collide, the zombie can actually hurt it.
So basically don't use the built-in link feature?