Block 1 Voltage Dropping While Sitting

2010 Prius 4

The car has sat for several months after an engine rebuild. Dr. Prius showed 15.4 volts on all blocks except block 1 which was at 6.3 volts. I measured the voltage on the block 1 modules individually. Module 1 had reversed polarity and Module 2 was at 4 volts. I decided to replace both modules. I purchased ebay modules that showed up with 7.8 and 7.9 volts and load tested perfectly. I ran the load test long enough to drain the voltages down to match the existing state of charge of the rest of the modules.

In the meantime, I moved all the modules two spots over so when the new modules showed up I could slap them on the end. So now what was modules 3 and 4 are now 1 and 2. The new modules are 27 and 28. I completed reassembly and pulled up the Dr. Prius the next morning. Block 1 is down to 15.0 volts after sitting overnight.

So I have one round of block 1 draining that killed two modules and it looks like the same thing is happening again. Does anyone have any experience with this problem? I'm going to investigate the sensor lead to block 1, but in my mind if that were grounded somewhere and draining block 1 then it would affect other block voltages as well.