CPU: AMD Ryzen 5 1500x (3.5 GHz)

Mainboard: ASRock A320M-DGS

GPU: GTX 1050 Ti

RAM: 16 GB

OS: Windows 10 pro

SOASE Rebellion version: 1.9 (with all DLCs)

A few days ago my PC broke down so I bought a new one. I had no problem running SOASE on my old system (Windows 7, AMD Phenom II x4 (2.6 GHz), GTX 650 ti, 8GB RAM) so I expected nothing less.

Turns out the game stutters every few seconds right from the start, to the point of being unplayable. I don't think it's a hardware problem since oddly enough the game runs silky smooth if I surrender and keep watching the CPU play, even on max speed and huge fleet battles occur between multiple AIs. The stutter only happens if the human player is still playing yet, doesn't matter if I just sit there and do nothing. Changing game settings has no effect, no matter if I play in low or ultra settings, windowed mode, or sound on/off, the result is always the same. 

GPU driver is up to date, tried running the game on a single core with high priority, tinkered with Nvidia settings etc. to no avail. I'm pretty convinced at this point hardware setting has little to do with it. It must be something related to player interface, like maybe the empire tree and such? Otherwise why would the game run smooth when only the AIs are playing, and stutter only when the Human player is alive?

SOASE is the only game I have with this problem, much more demanding games like Fallout 4 or other old games like Medieval II Total War runs very smooth. Anyone has an idea how to fix this?