Conveyers stops working in some simulations

Hi

I have a simulation in which a toy car is assembled. I created the workcell with two conveyors transporting the two parts to assemble. However, i experience that after running the simulation once, where everything works, the second time i run it the conveyors stop moving parts. I then have to completely close and reopen the workcell, see attached video.

An earlier version of the workcell still runs perfectly fine, even when stopping and rerunning the simulation.
I have experienced that this conveyor issue happens sometimes in other project, but i have never found the reason why and/or how to fix it. Even in projects with just one conveyor.

Does anyone else experience this?
Does anyone have a fix or explanation?

Thanks in advance!