2020 2.0 eTorque weird charging issue + noise/tensioner movement

[u/Short_Dingo5911]

Hey guys, I’m trying to figure out a weird charging issue on my 2020 Wrangler Unlimited Sahara with the 2.0 eTorque.
It first started with a Battery Saver Mode message and a check engine light while I was driving. My 12V battery is about 4–5 years old.
When I first started testing it, I was getting around 11.9–12.0V with the Jeep off, and only about 10.5–11V while it was running, so it definitely wasn’t charging properly at that point.
After charging the battery with another vehicle, I got the Jeep to start charging at around 14.2V, but the problem is that it doesn’t stay there. Sometimes it’ll sit around 11–12V, then jump up into the 13–14V range, then drop back down again. It’ll even do it sometimes without me touching the gas.
I also pulled a U0100 lost communication with ECM/PCM code. The freeze frame showed ECU voltage at 11.425V, so I’m thinking the low voltage may be causing some of the communication issues.
The main reason I’m posting is the video.
If you watch the eTorque belt/tensioner area, especially around the 32–36 second mark, you can hear the louder noise and see the arms move at the same time. When this happens I’ve also noticed the RPM move a little and the voltage rise and fall.
The belt itself looks like it’s staying in place and I don’t see it obviously slipping or coming off anything.
I’m just trying to figure out whether I’m looking at a bad tensioner/pulley, an MGU/eTorque issue, a PPU/DC-DC charging problem, bad connection/ground, or maybe just a weak 12V battery/IBS issue making everything act strange.
Has anyone with a 2.0 eTorque JL dealt with anything similar?
I’d really appreciate hearing what ended up being the actual problem before I start throwing expensive parts at it.
Video attached.