This sounds like its neurological relating the the spine and nerve compression.
I had a neck/cervical problem where I would start to get tingling then pain then paralysis that would radiate from my neck to shoulders down my arm to my elbows. I even got chest pain so it was difficult to breath.
The imaging showed degenerative disc disease, intervertebral disc protrusion and spondyllotic spurring with mild narrowing of the spinal canal. This went on and off for about 9 months until one day it did not stop. Normally I would recover in a couple minutes.
I took presdnisone for 3 days to reduce the swelling and muscle relaxers and prayed a lot for healing. Went for a recheck 2 weeks later and my doctor said he was surprised to see me walking and moving without pain. Anyway, its been just over a year and symptoms have not come back. Did you vet do imaging of the spinal cord? You might consider a CT scan or MRI.
Often after a seizure, you might get very tired or vomit. My daughter used to have them.