My CTC-16XL Project.

[old_tv_nut]

At this point it would be helpful if you had an accurate frequency counter and could measure the range of adjustment with L31 (A16) to verify that you are always on the low side or high side and cannot get nominal frequency. It seems that there must be something wrong with the oscillator circuit (wrong capacitor value or such).
C112, C118, or C114 would be prime suspects, or even one of the .01 bypasses (C110, C113), since you say the board was mangled by whoever had it last.