I had a similar problem. In my case, the needle would always point at 60
degrees until I was on top of the NDB then the needle would "seek" the
station. Once I got beyond 2-3 miles from the NDB, it would go back to 60
degrees. I later determined that it only happened when the strobes were on.
Come to find out, the power supply for the right strobe (located in the
front of the right wing) was leaking interference. The ADF seeked the
interference unless the NDB signal was very strong. I suspect was you have
a similar problem. It should not be much of a problem for a radio shop to
figure it out. Muncie (MIE) Indiana found my problem in about 15 minutes.

Kevin Chandler