The only thing i can think of is that you have played some chords that didn’t set a note-off but still occupying the notecolumn used for the note-on and as soon as you started record mode and added another note, it got automatically expanded to a note-column where no audio was yet playing.
Even if your instrument faded out, without note-off, the audio-column is not released for a new note.
But what did you do exactly before you set edit mode?
I am able to repeat this behaviour by switching on CS1x, starting Renoise, select sample, hit editmode and press a key on synth. I was suspecting there would be some setting in synth that could cause this so thats why also tried in factorysettings. It still maybe a problem in CS1x but I feel strange no-one has not encountered this before as it’s pretty common synth among us.
Also I now noticed that the cursor isn’t going down the pattern as it does when I press a note from keyboard, it should shouldn’t it?
I’ll be damned. I tried switching off Chord-mode from Renoise (did nothing else, absolutely nothing) and all seems to be working fine now… lines are advancing as normal and no more extra-columns. And whats even more strange everything is working fine even if I switch the chord-mode back on… so all what was required was to switch chord-mode off one time. I’ll start composing again after a few months break … can’t wait to get back home from work