Autistic/neurodivergent kid I babysit acting out and getting physical with me suddenly

I babysit for a set of pre-teen twins (let's call them X and E), and X has has behavioral issues. They're both very sweet and have amazing parents, but X is neurodivergent and acts up on occasion. I've been babysitting them since the beginning of the year. However, as of recent, his episodes are more frequent and I've been present or the target of them. Their mom has told me directly that they are both clearly very comfortable with me, which I'm glad to hear.

They have restricted screen time, but between the both of them, it can be extremely difficult to maintain that without directly cutting off power or getting them out the house (they do activities before I pick them up so that's hard to do).They make a very good team lol. They were only allowed to watch a certain thing but went behind my back and changed it and their mom got home basically at that time. That eventually led to X and her having an argument. He's was just very disrespectful and I was a bit shocked. It was a handful of other times he's talked like that, but never that serious/to that degree.

The next day, he wasn't allowed screens so I enforced that because rewarding that level of behavior is beyond me.However, that led to us having a physical altercation over his Switch. This has never happened and his mom told me he hasn't acted this way with a sitter in awhile. I definitely want to talk more with his mom, but I would really just love to understand what else I can do.