Question PC rebooting under certain load after upgrading parts

Dec 31, 2020
Hi all, hoping someone can help identify an issue causing my PC to reboot under certain types of load. I recently upgraded a few parts at different times but have just begun experiencing this now since replacing my GPU.

Black screen reboots occurring during Puget Systems Premiere Pro benchmark test (approx 8-10mins in) and also about 10 mins into playing RDR2 (and other games). I am able to replicate the issue during these specific instances, however when I am usually editing and exporting 4k content there's been no previous history of this issue happening. It first happened recently playing RDR2 with a new 3060ti installed. The issue didn't happen with my 1660 Super OC installed, which I replaced yesterday.
It would be easy to assume the 3060ti may be RMA/faulty however I have completed full benchmarks for the GPU and for the rest of my build with no problems. My temperatures are all pretty good too, GPU under full load on furmark peaked at 64c, whilst my CPU peaks at 72c during cinebench.

FurMark - 6746 points (112 FPS, 60000 ms) @ 1440p preset.
Cinebench R23 - 18,557 multi core score.
Memtest - All Ram tested until 100% with 0 errors.

GPU - 3060ti (tried both the latest Gaming and Studio drivers with clean installs).
CPU - Ryzen 3900x.
Cooler - Hyper 212 Evo Coolermaster.
RAM - 32Gb G.Skill Ripjaws V CL14 3200mhz using A-XMP Profile 1 @ 3200mhz with CL14 timings.
Mobo - B450 Tomahawk Max.
PSU - Corsair CX750M.
Storage - OS on Sabrent 1Tb NVME SSD, a 500Gb Sandisk Ultra II SSD, a 500Gb Samsung Evo SSD, a Seagate Barracuda ST1000DM003 1TB SATA 3.5" & finally a Seagate Barracuda 3TB SATA 3.5" ST3000DM001.
Case Fans - 2 x Corsair 120mm exhaust and 2 x Noctua 120mm intake.
Monitors - ASUS ProArt PA278QV 1440p & Samsung SMS27A350H 1080p.

I recorded the screen with my phone when I was able to replicate it, so you can see all the HWMonitor and Task Manager and GPU-Z information the moment it happens, there appears to be a slight spike in CPU voltage before the black screen, however the spike climbs to nowhere near it's peak voltage during cinebench for example. GPU also has a spike in voltage but power % is only around 50%?
I am hoping this could be diagnosed down to the PSU needing to be replaced, as it's now the oldest part of my build.
Any advice welcome especially from anyone who has experienced the same - not quite the start to life I imagined once owning an RTX card! My Sabrent NVME, Samsung SSD, CPU, GPU and RAM are all less than 2 months old.
I just ran Unigine Heaven 4.0 with high settings and experienced the exact same black screen reboot after about 4 mins, and with Modern Warfare I was unable to get through the menu without a reboot. I have tried limiting the Power in MSI Afterburner to 95% with no change of fortune.

For diagnostics, here are the Event Viewer results for the reboots:
Screenshot 1
Screenshot 2

Please help!
Dec 31, 2020
What make/model 3060ti ? Factory overclocked model?
CPU overclocked?

Remove all overclocks.
Set GPU power limit to lower value - 80% or even lower.
Hi it is the ASUS Dual OC 8gb 3060ti - I'll test an 80% limit now. I've not done any OC on it, only the small underclock mentioned and I also reset defaults in my Bios to see if that helped, but unfortunately it didn't.
I also have a Citrix display driver installed for remote work, thinking perhaps that might be interfering as it's using memory even while not in use according to HWMonitor