I am wondering, if Asus does not offer support even outside warranty. I have to pay for it for sure, but I would be more optimistic than with a local repair shop (not even knowing, where I can go). I even checked some shops for new hardware but prices are ridiculous.
But frankly speaking, I am still in doubt about the root cause.
University is quite a while ago and we did not dig into graphics cards design and VRAM, but RAM issues are usually not very deterministic as RAM assignment is not. So I do not think, that the first 2GB are always allocated on the good VRAM areas/chips and after breaching a certain limit, it starts to allocate the bad areas. But that is just a guess.
I tried to get some proof with "FurMark ROG Edition". It has an (very limited) option to allocate additional VRAM while benchmarking. So here is another video:
https://drive.google.com/file/d/1-NKzIAjZAwIIoXvOVfbYoQTo9eGrE8qS/view?usp=sharingFirst AoE4 is without FurMark running to have a baseline for comparison. VRAM usage is around 2800MB
Second AoE4 part is with FurMark running what increases the overall VRAM usage to around 4000MB. Neither the issues of AoE4 increased nor does the FurMark donut show any issues while rendering.
First Fortnite part is again just a reminder and a record for used VRAM which is around 2000MB.
Second part is a setting, which can be done in Fortnite which is named "Performance (beta)" (instead of "DirectX11" or "DirectX12"). That apparently works decently even with my battered graphics card. VRAM is between 1700MB and 1900MB.
Third part with Fortnite is running FurMark in background again (first started FurMark and afterwards Fortnite). VRAM consumption is now on 4000MB. A bit laggy, but no glitches. Even the bus is fine which usually leads to a crash.
I really do not want to keep you busy with this strange issue and am very grateful that you put so much effort in your analysis and suggestions already. So do not hesitate to stop here and just say: "It is broken. There is no workaround. Get a new one.". In the end, it is my curiosity that keeps me going after it. But this should not be your business
😄