Bed drops to bottom at start of print


I have a printer that has been working fine, however now when I begin a print it prints the raft then stops and drops the bed to the bottom. It doesn't stop, so you have to turn it off at the power or risk damaging the machine.

I have tried swapping the perfboard, as I thought that might have been causing the issue. But I would like to know what else could potentially cause this problem.

Thank you.

Have you checked all the connections? Like that the Ribbon cable is seated correctly 

Did you try several zcodes? Still the same?

Thanks for the replies. Not able to test further until tomorrow. But I'll let you know what I find. Hopefully it is just something silly like loose plug.