Sounds like your son. Is experiencing Refractory Epilepsy ( medications don’t work to their full potential ). I too have this. I’ve been on many different medications and non of them have worked 100% . I’ve had a left temporal lobe brain surgery
( helped reduce my seizure frequency from severe to mild and moderate ), attempted with the VNS ( didn’t work for me ) and the DBS . It’s working well and has reduced my seizures.

I have had my last 4 tonic-clonic seizures at night. They used to be during the day. Mine are considered breakthrough seizures and while the medicine controls my seizures for several years at a time, they are never completely gone.

I take 3 different meds, and just had 1 meds change. I still have seizures sometimes. (Complex partial seizures) I had 2 surgeries. Now I usually only have them in my sleep, maybe one during the day once in a blue moon. Sometimes seizures are super stubborn and med resistant. Definitely see if there is maybe other meds that could be an option if surgery is not something you want to personally put him thru, or is not an option for him right now. Meds that are helping both me and my brother (that has tonic clonic) is xcopri. It's a relatively new med. It may or may not need to be combined with other meds like I have to do. But you could ask your sons doctor and get their input on it.

His neurologist can try different ones. Sometimes a combination of 2 or 3 helps. If meds don't work, there are other treatment options. It's so hard to see our kids struggling tho.