Check Hybrid System

I have a 2013 with ~111k miles. Recently got the check hybrid system warning on with check engine light. Replaced the 12v auxiliary battery in the back and was working fine for about 3 weeks, now the code is back on.

When I brought it to the mechanic the hybrid cells seemed healthy, all running at about the same % but noticed its pulling a lot of juice from the 12v. Reset the codes again and hybrid battery is kicking in again like normal. I imagine the code will come back on again pretty soon.

Car runs fine on just gas but MPG is definitely hurting and with the small tank I have to fill up frequently now. I'm still able to drive it at 60-70mph on the freeway. Has anyone had a similar issue above? Wondering if I should just reset these codes every few weeks and avoid changing cars or having a new battery installed.