Shotcut has always worked great for me except for this video I have been working on recently. My issue is that on some of my transitions it says invalid but I found that lifting them and undoing fixes this. But if I try to export after doing so it crashes. It exports just fine if I don’t try to fix the transition but then I still have the invalid transition. I have the most recent version of Shotcut if that changes anything.
I wonder if you could try another work-around: remove (lift) the transition, and then create a new one by dragging one clip over the other (you may need to extend the clips first).