Haha, I just didn't know if it was intended or just an error.

I just had a game crash, I had an assembling plant selected and when I walked away it stayed selected, I tried the esc button aswell as Q and E to close it/switch to my inventory, my inventory aswell as the escape menu appeared on top of the assembling plant menu but they didn't cause the gui to dis...

So a problem I have been having is a glitch with my transport belts, I don't know exactly what is causing it but it can end up being pretty detrimental. They occasionally become blocked up at a turn like this one did as I was rebuilding my factory.