Last year I picked up my grail game, Monster Bash from a local collector. When I got to his place we removed the BG and there was a little fuzz on the batteries. No major leakage, just some light fuzz, we had caught it just in time. I got the game home, cleaned up the battery holder and didn't think a whole lot more about it.
Last week was the one week anniversary so down to the basement I went. When I removed the BG I was horrified by what I found. My theory is there was still some alkaline residue left on the battery holder and it slowly ate away at the battery. *sigh* Don't mess around with $3 battery packs, if there was ever any kind of leakage toss that baby right out and get a new one or install some NVRAM
So now to send this guy off to have some sockets swapped out a NVRAM installed.