Even if the class address was hard-coded,.
If you extended the class with FEBuilderGBA after adapting the patch first,.
I think that FEBuilder GBA will automatically rewrite the hard-coded class address.
The repoint of FEBuilderGBA also tracks the LDR instruction.
I agree with Mr. Jj09.
There is the possibility that animation is not set for class.
It might be a good idea to set something appropriate animation pointer.
I tested it with Promotion 3 branch patch that is attached to FEBuilderGBA.
First, adapt Promotion 3 branch, then extend the class.
And I set the class 0x80 ,set battle animation .
If you forget this, when you promote, the screen gets black and freezes.
This works correctly.