FYI, DocumentUltimate v3.6.0 (October 12, 2017) fixes this error:
Fixed: The below error which happened in some environments:
The type initializer for '_UXg' threw an exception. ---> Could not load file or assembly 'PortableEngine, Version=18.104.22.168, Culture=neutral, PublicKeyToken=a6f3cafa178e6038' or one of its dependencies.
The error happened either:
In both cases, the error is now fixed.
So you should not need the above workarounds.