Craig Smith wrote a very interesting post for Freesound. In it he explained how took tape with sound effects ranging from the 30’s and 80’s and restored them. The kicker is that one of those recordings was the Wilhelm Scream.
The biggest issue he had was a lot of these tapes had sticky-shed syndrome. This is basically a breakdown in the binder that holds the magnetic tape together. A common fix for this is literally baking it for some time and then playing it again. That is exactly what Craig did, he took the newly baked tape (after some cooling) and recorded it for later restoration.
After recording it he then went ahead and did the lengthy process of restoring it in Isotope RX 10.
Not only is one of those pieces of tape he fixed the Wilhelm Scream but you can even listen to the recording of it as well.