Well I can’t tell you why it’s crashing but maybe a solution would be to add another station (single line and small) next to where you want to upgrade your existing one. Not so close that it will interfere with your rebuild mind you. Once built group the original station with this new station so they maintain the same name and are part of the same line. Then remove the old one and rebuild it. Regroup it then remove the small temporary station.
I’ve done this to keep production from ceasing/being disrupted when it thinks the line is no longer there. I always PAUSE while doing this type of activity.
Maybe it’s the line being fully disrupted causing the crash.