Surface Book 2 GPU Driver disappears randomly after May 2019 update

Thanks for the reply, Entegy. 

I tried reverting back to V1809 as soon as I found out that this was an issue, but it was well past the 10 day window allowing the reversion from v1903.

I ask respectfully, how are you so sure the issue is in software and not in hardware?  I actually own 2 of these devices, and the first one - purchased February last year - had reported device driver loading/starting issues for the GPU when it was first started brand new out-of-the box.  So I can attest that the GPU on that device didn't work initially, which was well before v1903.  It did eventually load and operate normally, although I did wonder why it should have had such a problem straight out of the box.

It is beginning to appear this discrete 1060 GPU was grafted onto a system with an integral UHD620 display adapter, and that maybe it wasn't such a harmonious union.  Nvidia's website support doesn't address issues with this particular GPU directly, and they appear to have distanced themselves from it.  I've attempted to use their latest driver's nonetheless in the hope that it would fix this GPU issue, but instead it caused a hardware lock error on the tablet.  Only by rolling the driver back to 388.08 did the hardware lock error go away.  So now I'm back at driver 388.08 for the foreseeable future, which isn't doing any good since the GPU drops out of the device driver list anyway.

So after all that rambling, what to do?  Ask for a refund?  After all, they (Microsoft) broke the thing.

Because this specific disconnect issue only started under v1903 and reverting to v1809 fixes it. Microsoft itself says it's working on a fix on the known issues page. If it was a hardware incompatibility, then it wouldn't be fixable by software, which would be a disaster for Microsoft.

Problems straight out of the box can happen, but there are a ton of firmware fixes downloaded once you connect to the Internet. Unfortunately, the Surface line has a bad reputation of poor quality firmware at launch.

As for the "union" of the two graphics cards, the UHD 620 is in the clipboard part and the NVidia card is in the base. They are separate. I'm not sure about a "hardware lock". I've been getting my NVidia drivers direct from geforce.com. I'm now on yesterday's 436.02 drivers just fine, apart from the disconnect issue of course. I did find a workaround for games, which is to play them in exclusive fullscreen. Doing this doesn't cause the disconnect, furthering the proof that the issue is in Windows, as when a game has exclusive fullscreen, Windows passes control of the GPU to the game. This does mean you can't ALT+TAB out of the game because the dGPU will immediately disconnect.

What to do for now? Wait it out. If you want to fight for a refund, that is your right as a consumer. I was warning against fighting for a replacement because all Surface Book 2s will have this disconnect issue under v1903 until a firmware/software update comes out.

The only solution I have is to revert to the default company image of my machine and disable Windows Update, which itself is a massive security risk and I am very, very reluctant to do. This is costing me productivity and money. Microsoft bricked my GPU and are being slow to fix it.

You don't need to block Windows Update. If you can revert back to v1809 under Settings>Windows Update & Security>Recovery, it will stay there. Since you said it's too late, what OS build is your company image on? If it's v1903, I'm pretty impressed they're that fast at updating it. Not many companies move as fast as mine.

There is currently a block on Surface Book 2s updating to v1903 via Windows Update, so any new install of v1903 has been forced by the user.

Lets be clear: the throttling issue started BEFORE 1903. Microsoft just decided to acknowledge the issue now. I spent 40+ hours troubleshooting with Microsoft back in March/April before 1903 was available. I did try installing 1903 in May to see if it solved the issue and it did not. I have a strong suspicion the throttling issue was introduced in an earlier build or other windows update.