Scores freezing MuseScore when trying to work on them

What is wrong with some of my scores, like this one LGMVentura_example_CP1_III.mscz , that makes MuseScore 3.6.2 freeze whenever I do anything, like zooming, panning, inserting or moving a score element?

MuseScore gets irresponsive for about 30 seconds and then unfreezes again. It's impossible to edit anything having to wait half a minute for any command to respond. Most of my orchestral scores have this issue and the problem seems to grow exponentially as I add more stuff into the score. And this one is still pretty empty compared to other consecrated orchestral scores.