https://www.theregister.co.uk/2019/03/01/slow_ring_windows_10/

Having finally inflicted a 19H1 build of Windows 10 upon Windows Insiders on the Slow Ring, Microsoft has admitted that the minty-fresh test code has some problems.

Build 18342 was pushed out earlier this week, having spent some quality time in the hands of Fast Ring testers. The latter found themselves blocked if they were using certain Intel CPUs, something Microsoft swiftly fixed with Build 18343.