I have a similar issue when using multiple synced Scaler instances in a project. As I found out, the crash does not occur when I turn off OpenGL rendering with the ScalerSettings App. It would be interesting, if turning off OpenGL rendering also fixes the problem in your situation.
See here for ScalerSettings App:
My assumption as a software developer is, that when multiple Scaler windows are open, they try to update their window content at the same time when receiving the midi CC commands resulting in a crash, maybe because of some shared OpenGL resource.
The same could be the case when multiple Scaler instances are synced.