Could not load file or assembly 'Aspose.Pdf' or one of its dependencies. Strong name signature could not be verified.

When deploying web application with Aspose.Pdf we get the following error:

    Exception type: ConfigurationErrorsException 

    Exception message: Could not load file or assembly 'Aspose.Pdf, Version=8.3.1.0, Culture=neutral, PublicKeyToken=47b2d0fcacdd3eb6' or one of its dependencies. Strong name signature could not be verified.  The assembly may have been tampered with, or it was delay signed but not fully signed with the correct private key. (Exception from HRESULT: 0x80131045)

Exception occurs when running the web application. This doesn't happen with every deployment. Rebuilding and deploying again has fixed it every time so far but it is costing us a lot of time. Any suggestions?

Thanks,
- Mikko -