Phase Locked Loop

Trying to understand how this PLL in a ham transciever works.
https://www.mediafire.com/file_premium/sx3lig50i6eb2nq/PLL_UNIT.zip/file
Its not locking unless you are near the higher range of the VFO input and
spin the knob very fast, then it locks but only for a small amount of VFO freq
change.
There is a dual gate FET Q28 that is suppose to have 5Mc on each gate and the
gate from Q26 IC chip is the one with the proper signal.
I guess this is triggering the "unlock" / VCO -Off line to go active?