https://wccftech.com/microsoft-pulls-back-potential-windows-10-1903-release-candidate-from-slow-ring/

Microsoft released Windows 10 version 1903 Insider Preview Build 18362 to Insiders in the Fast ring on March 20. Just two days later, the build was offered to those on the Slow ring making many believe that 18362 would be the Release-to-Manufacturing (RTM) build. While the speed gave us hopes that major issues have been ironed out, the company is today pulling build 18362 back from the Slow ring after a number of Insiders reported installation issues.

Microsoft has released the following update today clarifying that a cumulative update sent out for a previous build was causing the issues for the potential Release Candidate (RC).