Hi Sharke,
I can certainly understand your annoyance there. I can honestly say that, in all my years of using the piano roll, I have never seen notes lengthening like that.
They appear to have almost, to within around 1/32nd of a note, edged up to the new note that you inserted.
Unfortunately, I am in work now, and I therefore cannot get on to X1 to see if I can replicate the problem, and it is more than likely that someone else will have solved your problem in the meantime.
For now, though, could you please check, and list all of your settings that you are using in the PRV. Settings such as Snap, which tools you have been using, anything you think you may have done up to the point of placing that single new note.
And were the four preceding notes selected at all?
How did you input all of the other notes up to this point? Manually, or with a MIDI keyboard?
Please hang on in there, and I, or someone else, will do their best to help.
regards
andy