I suffered a mini stroke just prior to finding out I had PD - this was known as a bleed to the brain - I feel sure that had some connection with my diagnosis. In fact I thought the initial symptoms were that of a stroke - shaking of left hand drag on left leg - I thought they had got my PD diagnosis wrong. It came as a shock. But luckily I have had no problems with the medication I am on Ropinirole 6mg per day.
Hope your dad is soon sorted out with some meds that suit him because everyone is different, I am sure the PD nurse or your dads consultant can help him out, or you can phone the help line at the top of the page for some advice.