Blue screen + missing GPU

I am using an XPS15 9530 with an NVIDIA RTX4090 GPU

I keep getting these issues and have done for a few months. I must have had this BSOD 50 times by now:

- For some weeks now, multiple times a day I seem to get atleast a blue screen error at apparently random times, where my laptop freezes and a few minutes later it says 'something went wrong :(', the stop code is: DRIVER_POWER_STATE_FAILURE, and it forces a restart.
- Inspecting the minidump files show is an issue with nvlddmkm.sys: ''*** WARNING: Unable to verify timestamp for nvlddmkm.sys''
- This BSOD always triggers the GPU to go missing from my display adapters as well. I can get the GPU back by booting into uefi mode, but the BSOD will happen again soon after.
- There appears to be no strong relationship between what I'm doing on the laptop and whether the BSOD happens. It can happen when I have one single word doc open, when I was trying to post on this forum earlier (only with chrome open), but it does perhaps seem to happen slightly more when running mulitple things at once.

Things I have tried:

- After BSOD I can bring the gpu back by booting into the uefi alone (smashing f2 at restart). However, BSOD will happen again soon after.
- Updating windows
- Updating all drivers
- Running the SupportAssist hardware scan and other tests
- I have tried multiple bios version, its still happening on the latest 1.12
- The full DDU uninstall reinstall route for the nvidia drivers
- Many others things I can't remember to write down here.

I contacted Dell support who have been no help so far (and actually recommend very poor counter productive measures imo):

- Round 1: Recommended I downgrade to bios v1.11 which I have just tried. The GPU has come back, but I as mentioned above often just booting into the uefi does this anyway. UPDATE: The blue screen error happened again within 1 hr of installing v.11. Back to dell support tomorrow I guess.

- Round 2: They are suggesting I reinstall windows. This is reallly really poor, that will take me days to reconfigure everything and I can see from others on similar threads has never fixed the issue. Can anyone say it did? I think its unacceptable they would be willing to push this kind of huge inconveniance on to a customer, knowing it will likely not work, a proper fix is needed.

- Update: Once again my GPU randomly reappeared the next day, towards the end of the day I got another blue screen error and its gone again.

More updates:
- Despite me pointing out on several forums that replacing the motherboard did not help, dell said it was the only thing they were willing to try. So we went ahead. After replacing the motherboard my laptop acted very difficult on restarts, it would: i) fail to sign in, ii) freeze at the sign in option. Eventually I got through.
- To resolve these issues dell support had me run windows updates and support assist scans and updates. This then COMPLETELY BROKE MY LAPTOP. Upon restart everything would freeze within seconds of turning on. Keyboard and mouse would work for a few seconds then go.
- Dell then said I need to do a complete windows reinstall. However, I asked before the motherboard if I should back up everything and they said the motherboard would not affect my data. Despite this I backed up most things. However, I will now lose everything I didn't back up.
- I said to support that their bad advice (which I said was bad advice as it hadn't worked on other dell community posts) has now caused me to lose data. They are responsible for this. Support gaslighted me very hard throughout the whole process and now haev said if I want that data I have to pay for a local technician to back it up first.
- I will have to do the windows reinstall. I then strongly suspect the BSOD/GPU errors will happen all over again (the technician who replacd the motherboard said this was likely). 

This is unbelievably poor from a laptop and support that cost >£3000,  and once again really poor support would so readily make me waste time on reinstalling windws. I'm using it for AI work. This has already cost me lots of stress and days of lost time.