Homebrew_PCBs

I currently use a GMP Mylam-12 Laminator for Press 'n' Peel work. I've come to try it today and found that as the copper board gets to the centre (front to back), the upstream RCD trips. I think it's when the load increases as it tries to pull the board all the way through.

Has anyone come across this before (with a laminator)? I'd appreciate any advice on where the issue might be?

Thanks again,
Phil.