So it turns out that RunOnce error happens at both x86 and x64 versions, tho I do not use RunOnce so its a bit confusing. But IE11 slipstreams into X64 Win7 with no problems, but fails with X86. Also tried previous versions of Win Toolkit that I know worked, and they also fail. I presume its something to do with new Win10 v1909. I will try on virtual machine that has W7x64 and see how it goes.