sansui 5500

If it works perfectly you should leave well enough alone. It is an over 50 year old component from a company that folded many years ago! But that’s just my opinion!!

Sansui made some of the best tuners in the world, this is one of their lower tier ones but still an excellent tuner if working properly. The issue is its old and will need restoration and alignment by now. old caps etc will cause issues and out of alignment tuner section will cause the issues your having.  lastly have you checked your antenna?