Is it safe to fly if you have seizures? mostly well controlled by medicine but still happens once in a while?

If you are asking about piloting a plane the answer is no. Having a seizure when you are the pilot in command can have disastrous consequences. If you're asking about being a passenger in a plane (commercial flights) that is safe as long as you're taking your medication. Having a seizure during a flight will trigger emergency response from the crew, however they are trained for such situations.

No contraindications to flying, as in commercial airlines, the compartment is pressured to sea level. The sole seizure trigger might be an emotional response. "Mostly well controlled" means to me that you have breakthrough events, and the control could be improved. Medications could be altered or adjusted, a vagal nerve stimulator could be considered. You cannot drive but can be passenger.