This is an odd one. I installed the mod normally on my singleplayer to try it out. Everything worked great in singleplayer. Thought it was cool so went to try it out on the unofficial I'm playing on at the moment.

Whenever I try to place a structure it fails to place (despite being green) and then often times places a different A+ structure out of my inventory.

I did this in creative so for example what I'm seeing:
Try to place Windmill, fails.
Try to place Workshop, fails.
Try to place Windmill, succeeds, but places the Workshop instead.

I don't have time to grab video tonight but if it doesn't make sense I'll try and grab some video tomorrow to better demonstrate what is happening. I've tried reinstalling the mod (locally and on the server) and fussing with the order, but same issue every time. I suspect the map doesn't matter too much but this is on Valguero as well.