There is a nasty bug when quantizing.
Play some notes
Use retrospective record to “record” them into the arranger
resize the midi event to a section with notes left and right in “midi event empty space”
move the midi file to the position you want
delete the excess midi notes to the right of the playable range of the midi event
-> You will notice that it moves all notes that were to the left of the midi region and places themon the first note of the region.
-> see video for a visual demonstration.: