I think you're thinking about the team-up with Lightspeed Rescue. There was definitely some issue there with Danny Slavin that led to someone else doing the voice for Leo in ADR, and I know for a fact that Trakeena's original actress was there, on set, in the Trakeena costume but she had to be replaced at the last minute due to some kind of contract dispute.

Yeah, I've seen every episode. Most of the later ones were super SUPER painful.

Linkara had said during his wildforce review that Danny slaving had a falling out with producers and that's why he's digitally inserted. I'd assume if was around the LSR crossover