Microsoft tends to stick to its traditional patch schedule (Patch Tuesday), and only rolls out an out-of-band update when there are serious issues for some Windows users or big security problems that need to be addressed. Microsoft's latest out-of-band cumulative update has been released for several versions of Windows 10, including the May 2019 Update (version 1903). This particular update is a required security update that "expands the out-of-band update dated September 23rd, 2019."
The update also brings with it mitigation for the Internet Explorer scripting engine security vulnerability (CVE-2019-1367). Microsoft notes that the security update includes quality improvements and calls out key changes, including addressing an intermittent issue with the print spooler service that could cause print jobs to fail.
One particular issue that affected users after the September 23rd update had to do with printing, and it has been addressed, with Microsoft writing, "Addresses an intermittent issue with the print spooler service that may cause print jobs to fail. Some apps may close or generate errors, such as the remote procedure call (RPC) error."
The other main fix addresses an issue that may result in an error when users install Features on Demand, such as .Net 3.5. The error seen in that instance states, "The changes couldn't be completed. Please reboot your computer and try again. Error code: 0x800f0950." Microsoft notes that for users who installed the earlier update, only the new fixes in the package will be installed on the device.
There are some known issues with this update with operations like rename on files or folders that are on Cluster Shared Volume potentially failing with an error that states, "STATUS_BAD_IMPERSONATION_LEVEL (0xC00000A5)." Microsoft notes that it is investigating reports that some devices startup to a black screen during their first logon after installing updates. It suggests turning the device off and back on again to remedy the issue.