Was given an old Vector LR 970 but it's experiencing a PLL LCK? error message

My relative gave me his barely used Vector LR 970 that has been in storage for ages and upon powering up it is giving me the PLL LCK? error message. I tore into it, looked over the board and couldn't see any obvious signs of bad solder anywhere and upon reassembly that the unit worked fine for about 1 hour and then as the unit got hotter that the PLL LCK error came up again.

Interestingly, this was repaired by Beltronics back in the day before he stopped using it for this very same error.

I know its quite old and probably not worth anything but it would still be cool to revive an old and highly revered detector its time. I think the only detector that was better than it was the STi that came years later.

Anyone here ever solve this elusive (and fairly common) problem?