R23 change yes and 18 ohms may be too low still.
Likely operating point, R21 may be too low.
Before you go to band pass filters try one thing... pain to install, Low pass filter between the junction of
pins 5 and 3 on t2 (IF port of the first mixer) and R27 and c16 (the junction of the RX/TX 45mhz amps).
The low pass filter is for 45mhz cut off I use .176uh (5turns on t30-6) and 68pf on each side (pi section).
This is the only thing that seems to help with the spur and enough to be ok if the drive is not excessive.
If the TIA is getting excess out of band or distortion the spur is bigger the filter helps (about 3-6db).
Sample size of one can't prove it. Worth a try if you can measure the results before and after.