You're adding a capacitor between ground and part of the tube when you
put your finger there. If the front end were tuned properly, this would
be detuning it. But it seems like it's improving the tuning, which makes
me think the tuning is way out. Look for open coils (easy to check with
a continuity tester), and bad ceramic capacitors in that stage.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."