LinearMover with Source Physics=Dynamic ?

Dear Forum,
I'm using RobotStudio 2021.2 (64-Bit) Version  21.2.9526.0.
I created a smartcomponet for a simple conveyor.
It contains just a source and a linear mover:

Both "Execute" I enable through the Porperties, while simulation is running.
It is working fine as long as the "PhysicalBehavior" of the Source is NOT in "Dynamic". It is working only in "none", "static" and "kinematc". But then it doesn't interact with the two plates, that have the "PhysicalBehavior" "static" (or fixed).

If I choose "Dynamic" for the source, I can see, that the "gravitation" is working and the box is falling down on a plate. When I execute the LinearMover now, the box is just shaking a little bit. I prepared two videos of the simulation, but cannot upload them here. 

If I use the surface velocity of the long plate and the "PhysicalBehavior" "Dynamic" in the source, it is also working, but unfortunately I don't know, how to start and stop it from external.
I just want a box moving on a conveyor, and if it reaches plate at the end, it should collide with it and stop there.
Does someone hase an idea, what could be the reason for this and how can I solve the problem.

If you need further information, please let me know.

Best regards