Thank you so much! That sorted it! Oddly enough, when starting a RWG map previously, I hadn't noticed that the game didn't go through the usual generation sequence - it just loaded up! Possibly using one of the RWG maps I'd used in A18. The mod doesn't seem to have any impact, which is fortunate, as I'm physically disabled & can't easily play the game without it. Thanks again for your help!
I've had exactly the same problem in a random gen map. Spawn in, trader distance in top right corner says 0.0km, but the yellow exclamation mark says 3km. Follow the marker, but no trader has spawned at the location. My output log: https://pastebin.com/j3j18ucv