ActionFaust
Mad Scientist
Did this character have a particularly complex design compared to the others? It's often the case that some characters will be CG to put less strain on the production. Big examples would be characters wearing armour like Berserker from Fate/Zero or Goblin Slayer. With so much detail CG is the best solution in the current state of the industry.Art was pretty poor apart from some of the character designs. For some reason they went with cg for one character, but not the rest! Animation wasn't great either.
And yeah I've heard that series ran into big scheduling issues towards the end. Signs of an industry that definitely needs more anime than they can handle /s