Thanks for your help with this guys,
I used the Restart button within the GUI and via the Windows Start button, same result.
The “problem PC” is a Dell Optiplex on Win 10 Pro, I will try the Shutdown -r -t 0 when I get back around lunchtime.
I am away from base this morning, using a different PC, a Dell Inspiron laptop which is still on V13.2.18.0 and doesn’t display a problem. I think I‘ll leave it that way for a wee while until the Optiplex situation is sorted.
Update later ….