Do you have anymore Steps? I wasn't able to repro this issue.
here is link to replay http://www.coh2.org/replay/46056/mg42-does-not-suppress
19 minutes you see the mg42 inside of a building but refusing to fire
22 minutes you see the mg42 again inside of a building firing very short bursts and can't suppress a mortar squad
27 minutes the mg42 goes full retard and can't even manage to suppress a conscript squad right in the open.
I think you need to recrew a mg42 to get this bug
How can bugs like this always ALWAYS slip into your builds?