Shortwave stations come in regular AM Brodcast band

I was recently given a large Panasonic AM-FM wood cabinet table radio of the late 60's early 70's vintage.I usually don't look for transistor radios of that era,but it was in nice shape and it was free you can't refuse a freebee.However it picks up shortwave stations on the AM band as well as all the other AM stations that I can pick up in my area and come in on the correct places on the dial and the FM works fine.I had an Emerson all american 5 tube radio that would do the same thing even after careful realiginment with my signal generator.Has anyone else run on to a problem similar to this?

It has to do with Image rejection, and/or might also be poor solder connections.