Problem solved, thanks to the fantastic schematic here
https://www.vintage-radio.net/forum/...ad.php?t=30889 found the oscillator transistor AF125 and replaced with an AF124 I had lying around.
Only once I'd put it all together did I realise that maybe the wiggling temporarily fixing the problem rather than tapping meant that perhaps the legs on the AF125 were just shorting where they were crossed ...
Oh well, I've now taken the module out and put it back about 9 times so can do it in about three minutes!!!!