I have played around with it again, elevating a point for a note on the expression curve for any instrument, then clicking on the note right after it. All the notes from the one that I clicked, on that same track, do not sound anymore. The note I changed the expression on still sounds and is showing the correct duration bar.
I enclosed an example screenshot. Note that the selected note showing a duration is the one note after the original one (the one at the beginning of bar 41, where the green line is) that will show a duration bar, and it is shorter than it should be. Very weird, but at least it is something somewhat reproducible!