[Hallicrafters] Tuning Question

[Gerald Adams II]

I recently purchased a model SX-99 that appears to be in very good original condition.  The only problem I'm experiencing is that the Tuning and Bandspread dials seem to get stuck (knob turns, dial doesn't) when turning in a clockwise direction.  It does not do this all the time and usually if I return to full counter-clockwise then it either doesn't stick or sticks in different position.  I am very new to this and have little to no radio expertise (but I'm willing to learn.)  I'm not sure what type of maintenance the radio has had in the past but it is very clean, just a little dust visible inside.  I have not yet figured out how to get inside the radio, it appears that two screws on the inside are keeping it shut.  This is my first posting so thanks in advance for any help.

Jerry