There is a big chance that after settling down for some time, the cube is going to sleep.
Normally, a collision would wake it up but I guess removing a collision does not count.
Unfortunately, I am new in UE but I’ve seen this behavior in other engines lot’s of times.
Maybe you can try placing the cube a little higher (so it falls when the game starts) and debugging it with onComponentSleep.
Looks like there was a bug about this and the last post in this thread says they’ve found a solution: Prevent rigid body from falling asleep - #9 by 123pirke