Here's the info from Reliablility Monitor for 1903 from my Production PC, which I use every day for 6 hours or more, 7 days a week. This machine takes a powerful beating and I use it hard (and I'd like to think well). Here's what Reliability Monitor says about this machine going back to May 31, the day I forcibly upgraded from 1809 to 1903 on this machine, using the Update Assistant at the Download Windows 10 page (to use it, click the "Update now" button at the top of that page):
Note that my reliability index is at a perfect 10. I've had three days with application failures and/or Windows failures over the 19-day period I've been running 1903. Errors occurred on Days 1, 2 and 7 in the graph.Day 1 includes two IAStorDataMgrSvc.exe errors (relates to Intel RST, fixed by installing new drivers), it also shows a Firefox failure that recurs the next day but not since (two new versions since then anyway)
Day 2 another Firefox failure
Day 7 Internet Explorer failure (don't use this very often, happens from time to time)
only serious error occurred this day: mouse and keyboard froze became unavailable so I had to forcibly reboot
not sure what caused this, but it hasn't happened for the past 12 days
HTH,
--Ed--