Allo Digione Sig and clean power problems

I’ve had my Sig for about a year. I power the clean side with 4 life4po batteries. Recently the Sig has started to fail when the batteries get to about 82%. The sound is almost like a skipping…not the same as insufficient data, but kind of similar.
In the past, these batteries were good for 6 to 7 days. Why would it stop working correctly at 82% of battery life? Anyone have ideas?