Help with Zenith M730

[tacitapprova]

I am working on an AM/FM/AFC Zenith M730 from around 1965. I have replaced the selenium rectifier and the paper and electrolytic caps. It sounds good, but I am still having one problem with the FM. The FM drops out repeatedly. What is odd is that if I switch to AM and then back to FM, the signal returns, until it drops out again. I am guessing that there is a problem with the band switch itself. I was wondering if anyone has seen this before or has any suggestions on troubleshooting the problem. Thanks.