Script compilation times

Script compilation is very slow. Often several minutes. Strangely it's relatively fast when in play mode.

This project is relatively simple 7 script files in total, plus AssetStore tools dlls. I can use the editor in the mean time, but when I hit play Unity waits until the scripts compile. There's not much more cpu usage compared to idle, no one of the cores work near 100%. I infer it's script compilation because new properties in script appear.

Is anyone noticing the same issue? My machine is pretty beefy (6 core w/HT, 32GiB ram, root on ssd).
Modifying a script in a new project is not so slow, about what it takes in playmode in this project.