Thanks Martin and Geoff.
Need to carve out some time to open her up and check stuff. Hopefully just a loose connection from a part of the crossover I can't see readily, or a cold joint or something like that. Bit disappointing not being able to listen fully now before stripping it all down prior doing the wood and recap etc. When I get the drivers disconnected I will take readings and label each driver accordingly. Just did that on different speakers (Radford M70) which is also requiring a wood restore and recap.
On the IMF the whole baffle can be taken off - so super easy to work on. The baffle is double braced so a great original build. Very solid.
Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)