Temporary fix:
Config files are in "C:\Users\YOURUSERNAME\AppData\Local\Indiana\Saved\Config\WindowsNoEditor"
Not sure which .ini file is the correct one, but I slammed these lines at the end of almost every ini file there:
[Engine.InputSettings]
bEnableMouseSmoothing=False
[/Script/Engine.InputSettings]
bEnableMouseSmoothing=False