The presets on the 3000 series are well known to fail over time and are very expensive to repair.Yes my 8 mini preset switches did fail, but were quite easily replace with ones I think I got from Farnell or Element14, RS Components from memory. They used the same on old TV sets
This sort of thing https://www.sparkfun.com/products/97
You kept the front chrome part. https://ibb.co/JvX36qw
Cheers George