During the spring, I would hardly open the BMS and glance at the batteries. But these days I check a little more often to see if okay to run mini split overnight.
The other evening I checked each battery bank. One said 82% SOC (Batt1) and the other said 93% SOC(Batt2). And when I looked at the amp draw, I realized that Batt1 was providing double the amps of Batt2 for the load I was pulling. I went to bed.
The next morning when I checked the banks, they were also charging at different rates and Batt 2 was charging at half as many amps as Batt 1. In Batt 2, cell #2 was also spiking voltage into 3.6V when the others were at 3.32ish(I don't remember exactly but it wasn't anything close to 3.4for any of the other cell. When I took Batt 2 offline with circuit breaker, all the voltages got real close again.
I figured there must be extra resistance in Batt 2 and I took off the busbars connecting 1>2 and 2>3 and cleaned up all connections and that fixed the whole problem.
Its always some variation of this and first evident on the BMS check.