Hello Gilles. I hope you’re doing well these days.
To add to what Roger said, make sure Quantize to Frames is enabled and that the events start and stop on a frame boundary. To see if this is the case with your events, zoom in on the event, place the cursor at the beginning or end of the event and use the left or right arrow to go forward or back one frame. If it doesn’t end up where its supposed to (i.e. the cursor isn’t where it’s supposed to be), trim the event so that things are back to normal and your problem should be solved.