6950 XT stalls out under load — hotspot delta has gone from 23C to 30C in two weeks. Repaste, or is the card cooked?

Been fighting this for about a week and I'm running out of ideas, so looking for some help before I give up. Below is a vid of what happens - its usually worse and crashes after. https://streamable.com/4fgfbj Playing monster hunter world, everything fine for anywhere between 5 and 45 minutes, then the screen starts flashing bands. Frame rate tanks. Give it another minute or two and the display drops out entirely — no signal — but the PC is still running, fans spinning, audio usually starts looping. Sometimes it takes the next boot with it (BIOS shows fine, then no Display Port signal at the Windows handover, safe mode always works). GPU sits at 98-99% utilisation the whole time with clocks and voltage completely normal, but frame time climbs from 6ms to over 100ms while memory controller load falls from 60% down to 5%. Board power drops as it does less work, temps go down. Nothing throttles. Nothing gets logged. No WHEA. No bugcheck. I capped frame rate to 90 (about 217W board power) and it ran 22 minutes fine. Bumped the cap to 120 (about 280W) and it died 12 seconds later. Did it again, same result. One time it started degrading and I walked into a less demanding area and it recovered on its own and ran fine. Core Hotspot Delta Power 16 July 69C 93C 24C 341W 17 July 66C 89C 23C 322W Now 69C 99-104C 30C 320W So the core-to-hotspot delta has gone from 23-24C to 30C at the same power. Memory junction sits around 83-85C now, hotspot averages 99C in game. What I've already ruled out: PSU — logged everything and cant find anything out out the ordinary. DisplayPort cable — replaced CPU overclock — removed entirely. MPO — disabled via registry OCCT 3D Adaptive error detection — zero errors OCCT VRAM test — clean Full DDU + clean driver install with Windows Update blocked from installing its own display driver. Versions match. Crashed again anyway Browser hardware video decode off (verified 0% on the decode engine) — got two clean sessions then crashed again Specs: PowerColor Red Devil RX 6950 XT (running the Silent BIOS) i7-9700K, stock MSI MPG Z390 Gaming Plus Corsair RM850x, three separate PCIe cables to the card 32GB DDR4-3600 Adrenalin 26.6.2, Windows 11 Card is second-hand, bought a couple of weeks ago, ran perfectly for about 50 hours before any of this started Has anyone seen a 6000 series card develop a rising hotspot delta and start stalling like this, and did a repaste actually fix it? I've got the stuff fro a repaste but i might be able to return it still. Also open to being told I'm wrong about the thermals entirely and it's something I've missed. Thanks, any help is appreciated.