Help! Thunderbolt dock seen, but ports don't work, no attached devices seen.

Hello All,
I should preface this by saying that the computer in question here has a very long history of problems, and has never really been stable for more than a couple months. It was purchased from a system builder who (apparently) did a terrible job, and then along the way a whole bunch of people, more or less competent, got their hands on it and did all sorts of things to it, for better or (usually) worse. The most recent modification was that I removed a (completely) mismatched RAM kit, and one of the GPU's (it had two 3070ti's...not sure why or what they were trying to accomplish).

I have been pulling my hair out over a friend's computer (mainly used for livestreaming and editing) which bricked its windows install after a failed update (he might have hard powered off during the update... he is not sure). I used a windows install/repair disk to uninstall the update, and it worked well for a week or two. Then a couple days ago, he got a thunderbolt dock to connect a couple cameras and an audio interface. I had to install the thunderbolt drivers and turn off the security in the BIOS, but once I did that, everything worked perfectly. That was Tuesday. I got a call yesterday afternoon saying that nothing connected to the thunderbolt dock was working. I came to investigate, and while the thunderbolt dock was showing up in the "thunderbolt control center" app, the computer refuses to see anything plugged into it.

I updated the BIOS and made sure all the settings were correct, and when that failed I did a clean install of Windows 11 Pro, which also failed to change anything. I can't seem to find anyone with the exact same problem online, and I have tried everything I can think of. I also plugged the dock into my XPS 13 and it worked beautifully, seeing all the connected devices instantly.

The computer:
Gigabyte X299X Designare 10G (has 2 onboard TB3 ports)
i9 7960x
64GB of DDR4 (Kingston I think?) running at 2400Mhz with XMP disabled
RTX 3070ti
Random assortment of SSD's and HDD's, boot drive is a Samsung 970 Pro
Corsair AX1200i
Windows 11 Pro

The dock is a QGeeM TB4 Pro (I use the exact same one with my laptop every day and it works beautifully), with a 6ft cable matters thunderbolt 4 certified cable.

Any help much appreciated. I have pulled my hair out so much over this computer...I can't wait until it goes.

Did you manage to resolve this problem? We have the same issue now with a Dell Precision 5570 & WD19TBs Dock. OS is Win 11 22H3.

All drivers from Dell are updated but no joy.