Comment 7 for bug 1756995

Unfortunately, it does appear to be MacOS only as well; I tried on my Linux machine and can't reproduce.

My guess as to what is happening is that the dialog isn't working properly in MacOS and thinks that you have entered new values for the track start/end points when all you have changed is the width.

Unfortunately I don't have my Mac machine with me right now so I won't be able to hack on this today, if any of the other Mac-having devs want to try to fix it, maybe you can find it first.