Midi 'ghost notes'

[DJ-Spol]

If I look in MidiEditor after I have recorded a midi track, then under each note is another small note.
(please see image, I have dragged the 'real' notes down to reveal the small unwanted notes beneath them).
I have tried using 3 different brands of keyboards as source, but the problem is the same. How do I prevent this?
Setup: Win10, Protools 12, Focusrite interface.

[albee1952]

I've seen this when I had a keyboard that was connected in both directions(MIDI from the keyboard, into PT and MIDI from PT back to the keyboard). Unplugging the return solved that one. Next, look at the track you are recording onto and see if it is feeding midi out, and change that assignment to a VI plugin(it may be defaulting to ALL for both midi IN and OUT)

[elicious]

Select all midi notes,
then "remove duplicate notes"
from the pull-down...

[DJ-Spol]

I have only got midi out connected to the keyboard.

Thanks for pointing me to Event / Remove Duplicate Notes, that does make it easier than moving every single note, and delete the one behind.

But I would still like to find the nature of the problem, and how to prevent it from happening.