Please download v2.1.6 from this link:
link is removed as this version is live now
Reference both GleamTech.Core.dll and GleamTech.DocumentUltimate.dll files from this zip in your project (remove older versions and nuget packages) and let me know if the problem is completely fixed or not.
After you confirm it's working, v2.1.6 will be also available on Nuget shortly.