Hi John,
Most keys stick for a number of reasons:
1) The hole underneath has become tight and you need to use a 'key easer' that piano tuners use. These crush the wood accurately alowing the key to ride on the pin.
2) The felt underneath is dislodged and the pin is riding inside the wrong bit
3) One pinchroller spring is catching another. Check alignment
4) The key is warped and will need judicious sanding to stop it interfering with the adjacent key
5) The key pin is too far forward or too far back and is not central to the hole in the key.
If you swop around the pinchrollers then you will need to adjust the white keys for level using the back woodscrew in either the left or right position.
Best,
Martin