Physics simulation not correct when changing constraint linear limit (debug project included)

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Setup is like the following:

C1 is a cube, on top side, not simulating physics.
C2 is a cube, on the bottom side, simulating physics, enable gravity.
A Physics Constraint that links two cubes, with linear limit = 200, so C2 would just free fall to the ground when the game begins.

In the game tick, I gradually decrease linear limit to zero, the intended behavior is that C2 gradually move upwards, until it hits C1, but the real behavior is that, C2 stays still on the ground.
But, if I move C1 or C2 a little bit, let C2 come off the ground a little bit, then the simulation would be correct, i.e. C2 is going upwards.

Please check the project included for more details.
Just hit play and eject, select the actor Cubes and you can see the outlines of physics constraint.
Watch the green line decreasing it’s length, as the green line become shorter than the distance of C1 and C2, C2 still stays on the ground.
All codes are in the BP “Cubes”, thanks.

project included, oops


I have reproduced your issue in the project you’ve provided. I have found a solution to the problem that you are experiencing. The problem seems to be that when your cube hits the ground, it sleeps, as physics objects do when they connect with the ground. So what I did to remedy this was add a Wake Rigid Body node for C2, and this solved the issue on my end. Give that a try and let me know if it works.

Here is a screenshot of what the setup looks like now, for your convenience:

Have a great day

Thanks Sean, this works!