Hi @klayoutmatthias,

Klayout crashes in debug mode when a drag-and-drop operation is too fast compared to the pcell's runtime.

To reproduce press down the mouse button on a "slow cell", drag it to the layout and release the button before the cell appears. I've added a sleep call to the Circle pcell sample to make it slow enough. This also happens with the latest KLayout compiled from master.

An obvious workaround is to be patient with the mouse button :)

Thanks,
David