When moving a midi note with mouse I have always been in habit of holding down the Control key when selecting and moving. This is a known function to prevent moving the timing position of the note whilst being able to drag it to a new pitch.
Since 11.0.20 - holding down Control on the keyboard and selecting the midi note to be moved in Key editor causes the note to be locked from moving AT ALL.
However if you select the note without holding alt and fitst start to move it and then hold down Control on the keyboard it snaps to its original timing position - which is what you want.
Something changed with this in 11.0.20 and I believe this to be a bug. Perhaps those here can test this on systems and see if the same experience is had and confirm the change in MIDI editing behaviour.