Film advance. I bought a seagull 4a-105 camera and the film advance never seems to be consistent.

Question

I bought a seagull 4a-105 camera and the film advance never seems to be consistent. Often times the frame counter numbers are not centered in the viewing bubble. When I go to have the film processed, I have had as many as six to seven frames either double exposed, or no exposure in the frame. The best that I have managed out of 12 frames is 8 frames done correctly. I followed the directions and threaded the film to where the arrows align with the marks, but still the problem persists. Is the film winder the culprit? If so, how can I repair it? The camera cost me $217 new, and I can't justify spending $200 to repair it when I could buy a used Yashica online. Any help or advice is appreciated.