Hybrid Battery problems from lack of driving?

Due to the current pandemic situation, I have not been driving my 2013 Prius as much as I used to with working remotely, so essentially, my commute went from driving ~60 miles on a daily basis to barely hitting 50 miles a month. So the car has been sitting parked for a while. However, roughly two months ago, the car had given me the glorious red triangle giving me the P3019 and P0A80 codes. The usual engine was running non-stop and the hybrid fan in the backseat was roaring. I initially figured it may be due to the car sitting for nearly a month, so I cleared the codes. I have recently been driving the car a bit more (and by a bit, I may be now averaging roughly ~200 miles per month instead of 50 ), but this morning the dreaded red triangle came back. This time, I noticed it came back as the cars AC was on (though, it wasn't a hot day, just had the AC on just due to habit). However, the codes that returned were only P3019 and no P0A80.

I was wondering, can it simply be because the car is not being driven as much one of the blocks (or cell) just got weak? I have done cell replacements before, however, I was curious if it also made sense to see if the problem can be something else since the car hasn't been driven as much. The hybrid fan blowing did catch me off guard as I never noticed it being that loud when the red triangle came on, so I was wondering if perhaps that can be a problem? Otherwise, I am not sure what else I can really do other than tearing open the battery pack and start measuring every single cell and see if it needs to be replaced and re-balanced. Of course, I am open to other ideas here. The car is sitting just at 180K miles and on the original battery.

 

I actually replaced the 12V battery from the Toyota dealership back in January, and I have already cleared the codes (and red triangle).

 

I am a bit skeptical on the 12V battery being the culprit here mainly because I do own two other Prius's and another hybrid (Ford Escape) and they are being driven far less than usual and it isn't a problem for those cars. I should also note that this car does get driven at least on a weekly basis (all be it, maybe a 20-25 mile round trip for some errands). Also, if it were the 12V battery, is there any reason it would give me the 'P0319' DTC? Shouldn't it give me another DTC related to the 12V (I am pretty sure there is a DTC specific or related to the 12V battery)?

Nonetheless, I did decide to see if I can physically spot anything unusual in the 12V and Hybrid Battery area, as my intention was to get a reading on the 12V battery as it hadn't been turned on in over a day. We just had some rain here very recently (it was actually a bit stormy), and I realized I saw some water drops on the bottom of the 12V battery area. I decided to then do a test to see where the water may have come from, and it looks like the tail light area is the culprit (looks like the seal to house the tail light isn't doing its job), so I am now working on fixing that problem. However, no idea if this is even related, or I just discovered something new... lol.

 

Yeah, that is something I have noticed from owning a Gen 2 and Gen 3 Prius (not sure if it is a problem for Gen 4) that the water likes to seep in weird areas in the hatch area. I remember a Prius I once was looking to purchase where the water was literally dripping (albeit in super tiny drops) from the areas that where the corners are welded from the factory.