This one is easy to reproduce.
- Go to the ship builder
- Change to any alliance cruiser hull
- Click on a module button other than weapons
- Click on the weapon module button
- Switch to a non-alliance cruiser hull (I tested it with Valkyre)
- Click on the “Fusion Torpedo” weapon module
Steps 3 and 4 aren’t always necessary, depending on whether or not the weapon modules for the alliance cruiser have already been reloaded. These steps just for it to reload.
It looks like it is happening because the module screen isn’t reloaded when you switch between ships of the same hull class, even if they are of different races. Click on the module not available to that race and ‘boom’.