[Kenwood] Tuner problems on my 940

[Marc Bruvry]

Hello Group,
I just acquired an MFJ 259B and am astounded by the poor SWR on my
antennas (Cushcraft R5000 Vert, A3S Tri Bander (not too bad) and  Home
Brew Dipole). In trying to tune them thru the MFJ 962D tuner there seems

to be a "jittery" response. Like the coil arm has a rough surface.
(capacitance is liquid smooth of course) There is no visible appearance
of anything wrong and I'm wondering if there is any spray or paste that
might help the contact (like WD-40 or the anti-corrosion paste used on
antennas during assemblage.) I don't want
to put something on and find out that it was "a real bad idea"!
73, Marc / KF6VNT