Blueprint properties being reset after changing BP

I have a BP based on a C++ file that has an array of AActor*s exposed to the details panel. Some times, when I change the blueprint that the objects in the world are based on, this array is reset. However, it is not properly reset, it remembers the size, it just forgets what is in each entry.

This is irritating as I have to keep resetting the level to get the values back.