Need advice: Weird MIDI problem in REAPER

[SimonTaddio_Qc]

Guys,

My roommate has got into REAPER, and he came to me with a question I couldn't figure out.

He's basically trying to record MIDI tracks of his keyboard parts. It was all good since today when he had a weird problem that, as a PT user, I couldn't figure out at all.

From what I know, he recorded a MIDI part, then when he tried to copy and paste it right after the recorded riff. But between the 1st riff and the 2nd (pasted one), there was some kind of grey vertical line. The problem is that if he tries to delete or change some MIDI note in the 2nd riff, it also changes the notes in the first one too.
I'm pretty sure the grey vertical lines have something to do with that.

Anyone has any clue on what's this about?

I'll try to post some screenshots if I can

 

[narcossintese]

This vertical line is a MIDI controller message. Open the MIDI on the editor and click on this menu of the pic. The controllers with data are marked with a black dot before the name. Check them and see what exactly they are doing. You can also press "Alt + 3" (View > Mode: Event list) on the MIDI editor to see all the MIDI events on a list, and sort them by type.