Before downloading anything, use your game launcher to check for missing files. This is the safest way to restore the DLL from an official source.
The version initially shipped with some games was reportedly unstable, causing extremely long shader compilation times, memory leaks, and frequent crashes. oo2core9win64dll exclusive
Search your SteamApps/common folder for oo2core_9_win64.dll . Before downloading anything, use your game launcher to
The community found that replacing the "bugged" version with a stable one from another game (like ) often fixed these performance bottlenecks. Where to Find a "Good" Version Before downloading anything
Let me know, and I'll give you a precise answer.
: Right-click the game > Properties > Installed Files > Verify integrity of game files.