I've got a 8920B rf comm test set that we received for cal with a inop display. replaced Crt drive board and display worked. finished cal sent back to customer. unit shows back up a week later with same problem, resat all boards and was working again. a few days go by and its back with the same problem. narrowed it down to reseating the processor board being the problem, but after looking all over the connectors and everything theres nothing that stands out. Any ideas as to what could be causing it? I dont think its coming undone as it requires quite a bit of force to get it out and we've tried to replicate shipping and unit worked just fine after. Any help is appreciated, Thank you.