12.5 isn't great.
While you are waiting for your replacement Arkpak, I would suggest putting the battery on different charger and see if you can get it back to 12.7-12.8. Then let it sit for at least 12 hours with no load on it and check the voltage again, it should still be the same. If it's dropping down you may have to go through a drain/charge recovery cycle to get it back up to snuff.
Lots of threads on this issue, just went through something similar with a pair of Diehard Platinum batteries and was able to recover them.