Can’t listen in detail at the moment but as I recall the compressor on the old OS’s used to squeal for certain settings. If the compressor is off, then it must be the output and you will have to send it in or take it to a tech.
Sorry for the really slow reply but that is not the old MD compressor squeal sound. The compressor used to go eee-eee-eee with every big hit with a lot of bass in it. Absolutely the most horrible compressor you have ever heard.