Bug with Sith Eternal Emperor

Looks like this happens with any character that changes to become a "new" character when paired with Great Mothers. SEE and JML are both affected when using their ult, and I presume GL Ahsoka would be as well.

It's likely because she's a "Large Character" which prevents a team of more than five (no summons), and it's coded so that pre-ultimate SEE, JML, and GLAT (presumably) are different characters than post-ultimate versions, so using ult would push beyond that five characters limit.