Hello Scott and welcome to the Forum!
Are you using an in line fuse holder or do you have the power wires connected to your fuse block?
In case you have an in line fuse holder, check there as well if everything is tight and without slag. Some of the older types where the fuse is hold in place by a spring the springs tension might be not enough and cause power loss when a hard hit occurs.
I suggest to use an ohm meter and measure the continuity of the power cord while rattling and shaking it to simulate hits or vibrations.
Another thing: Check if the power plug is sitting correctly in the cable collector.
I heard of cases where this wasn't the case and caused trouble.
If you cannot find anything wrong there, bent the pins of your cable plug ever so slightly outwards to make sure they have decent contact in the socket of your unit. But be carefull there and don't bend them too much! If you bend them too much, they will not slip into their places in the socket and you might brake them if you force the plug into the socket.
Good luck and regards from Germany
Harry