Anytime he's in a scene that requires serious, dramatic acting chops? Or worse yet, anytime he's required to do a fight scene? Which you know, is an AWFUL LOT of times considering that this is a martial arts fighting show? He's among the most unnatural, awkward, uncomfortable, stilted, unconvincing embarrassments amongst the ENTIRE cast by far. Not a DAMN word out of his mouth that has to be delivered with anything approaching seriousness or gravitas comes within lightyears of sounding convincing. He STILL to this day, when doing fight scenes, sounds like someone struggling with a massively crippling digestive issue.
Let's illustrate this issue with the scene of Goku going SS in Kai:https://www.youtube.com/watch?v=2om9tJsswKI&app=desktophttps://www.youtube.com/watch?v=xsalzwkykIg
I don't like Nozawa's voice at all, but notice the noises throughout the scene. They're there, but they're very faint and subtle. It sounds like she's choking down genuine sobs of grief and anguish. Less is more. She's, you know... acting. Inhabiting a performance, in a moment of intense grief. Her voice sounds like a dying cat but she's displaying basic performer competence.
Over on Schemmel's end, in Kai (the "tremendously improved" version); he utterly FAILS to convince emotionally because he's, seemingly pathologically at this point, fundamentally incapable of conveying subtlety and nuance of emotions. Instead of subtly choking back tears, trying to stifle or muffle his anger... he's "Ygggggh!! RRRRGGGG!!! CONSTANTLY!!! UUUUGGHGHGHD!!!! MAKING!!! UUUGHSHAGAGGA!!! RIDICULOUS!!! AAAAAAAFFHFFFHFHFHGG!!! NOOOOOISES!!!"
He doesn't sound like someone who is genuinely in immense grief and rage. He sounds like an over-acting hack. He literally sounds like he's tweaking on meth or something. It is totally unnatural and painfully forced.