Aurora R10, overheating CPU but not really

So I've been struggling w/my son's Aurora R10 for the past few months now where it will more often than we'd like refuse to start up properly because the preboot system performance check will complain that there's a problem with a fan.  Our system has the AIO unit so it's not air-cooled. When it first happened it was complaining about the front fan so I went ahead and just replaced the front fan w/a Noctua NF-P12. We thought that would be the end of it but then we started getting complaints about the top fan. So I went and replaced the stock top fan w/2 Noctua NF-A12x25 in push/pull config. I also originally connected both to the top fan header w/a Y cable since that's where the original fan was connected to. But after a few days I thought I'd split the 2 fans up and not use the Y cable so I connected one fan to the top header and the other to the previously unused CPU header. And it seemed to be ok.

But more recently we've been getting complaints about the CPU fan for seemingly no good reason. Even if I went back to using the Y cable and left the CPU header empty it would still complain about an issue w/the CPU fan. And it was completely random. At one point I plugged the AIO pump into the CPU header and both top fans into the top header via Y cable and it still didn't work. But after an hour or so my son said it was working fine again. Like what the heck. I don't think the computer is actually overheating cause the problem seems to pop up randomly whenever he turns on the computer in the morning. He turns it off at night so it doesn't disturb his sleep.

Whenever we get the CPU fan complaint from the preboot, if we let the system continue booting up afterwards, the CPU is throttled way down and if we look at the CPU temp in Alienware Control Center it just shows 99 degrees C which obviously can't be right cause the computer's been off the entire night and just got turned on.

If we hit esc to bypass the preboot check it seems to boot up ok but if I launch ACC and try to switch to the Fusion tab the computer crashes immediately and turns off.

We have the latest BIOS, Win11 and Alienware-specific updates all installed so I don't think it's an issue from that angle.

So anyone have any idea why this might be happening? Do we need a new mobo or something? I was thinking of maybe replacing the AIO w/a Corsair but like even today the computer's been running fine. If I look at CPU temp in ACC it hovers around 40-60C which seems ok I think? I guess another question would also be how exactly should my fans be plugged in to the headers? One to top, other to CPU and pump to pump? Or should I use the Y cable and connect both top fans to the top header while leaving the CPU header empty since that's how the original one fan was connected? Right now the AIO is connected to the CPU header and the 2 top fans are connected to the top header. I've been loathe to move things around again since it's been working.

Any ideas/tips greatly appreciated and TIA.