Well it was nice while it lasted - EFI Boot options seem to be broken
So this is my first post and I'm having a bit of an issue with my gaming box. I have a suspicion that it has something to do with a minor windows update to troubleshoot some bluetooth issues I was having but I'm probably wrong.
The problem I'm running into is that my system did work just fine for about two months (Gigabyte Gaming box RX580, rMBP from 2015), where you boot with the eGPU attached while holding Alt-Option, select the EFI BOOT partition, boot to windows via that menu and then unplug and plug in the eGPU's TB cable during the windows logo loading screen. The issue is that since last night, if I restart the computer with the eGPU attached, the boot options (Mac, Bootcamp, EFI) never appear. If I boot with it disconnected, select EFI, and THEN plug it in, the whole thing freezes.
What's odd is if I boot into OS X High Sierra with it disconnected, log in, and then plug in the box, it works without issue. I couldn't hotplug it like that before. I'm just not sure what's going on here.
Format the automate-eGPU EFI partition then copy a clean EFI folder to it and see if that helps.
You could do what @itsage said and then redo the Bootcamp partition and prevent Windows updates. If you could get it to work just by redoing your Bootcamp partition, I can help you prevent the Windows updates.