Twinmotion very slow viewport

I’m jumping straight into Twinmotion with a design from Sketchup. The SKP file is 150mb and not particularly unweildy, but when I drop it into Twinmotion the program is so slow as to be considered unresponsive. The included demo runs fine even on ultra setting.

I’m running a system with dual 10 core xeons, 150GGB RAM with RTX 2080 & 980TI cards as well as multiple large SSDs so I am pretty sure it’s not a hardware issue. Any thoughts? Thanks.