Duratrax intellapeak false charging

I started charging them again and I was cheaking the voltage and one said 9.3 volts and the other said 9.0 volts. A couple minutes later I cheacked it again and the 9.4 one was blinking, so i checked the voltage and it said 8.0! Why??????

Another 10 min. and the blinking one drop agin to 7.9 volts!

Another 5 min. and a switch the 7.9 battery went back to 9.1 and the other one is at 9.4 now? Weird


So What ive been doing is switching the batteries back and fourth so the will both charge.