Opry99er, Acadiel posted the production test routines that MG used to run on all new GKs. I would use that to check out your unit. It runs through all of the RAM and does an extensive test. Also, there was a modification that MG put out because some units were prone to losing "bits" of memory when the GK was pulled out of and reinserted into a console with the power on. It involves a diode, resistor, cap change on the lower board. That is also posted.
Yep, find the GK archives that I scanned in... the sheet with the 'repair' (just a few components you have to swap out) is in them. We probably want to get someone like Mainbyte to put it on his page since so many people hit his page.
Also, double check the battery holder. I was getting intermittent contact; fixed it by bending back the top + metal piece on the holder by pushing it in without a battery. Between that and replacing the three components, mine seems to retain stuff well now.
If I'm not mistaken, it was the three parts that I circled that I replaced (enlarge the pic to see them - circled in red).