Wendy...my Frog came with copies of articles written by the very knowledgeable J.L.Linsley Hood - he goes into great detail of the innards and alignment of most of the tunable bits. The articles were in the "Short Wave Magazine for September and October 1981 - he goes through quite deeply the need for good alignment of the 54.5 to 55.5MHz first IF bandpass filter and then emphasizes the need for good alignment of the 52.5Mhz selective amplifier.
Aha - lookee what I found...
https://worldradiohistory.com/UK/Sho...WM-1981-09.pdf
https://worldradiohistory.com/UK/Sho...WM-1981-10.pdf
Hope your Frog now turns into a handsome Prince....