To resolve issues in the v6.13 OData client assemblies, Customer Support may ask you to apply hotfix CD_8.1.1.3556 (or later) and upgrade to the 6.15 versions.

One of the errors which *may* indicate that hotfix CD_8.1.1.3556 should be applied as below.

Exception:An error occurred while resolving evidence using the Context Service. at 
Sdl.Web.Tridion.Context.ContextServiceClaimsProvider.GetContextClaims(String aspectName) in 
C:\TeamCity\buildAgent\work\531db7af87a3c68e\.deploy\source code\web application\Sdl.Web.Tridion\Context\
ContextServiceClaimsProvider.cs:line 83
at DynamicModule.ns.Wrapped_IContextClaimsProvider_636fb58ffcf4498596af4853b9e0d872.
<GetContextClaims_DelegateImplementation>__0(IMethodInvocation inputs, 
GetNextInterceptionBehaviorDelegate getNext)
2017-05-14 19:27:41,338 [18] ERROR - Error thrown while showing Server error:
An error occurred while resolving evidence using the Context Service.
2017-05-14 19:27:41,374 [10] ERROR - Exception:Failed to execute query at Sdl.Web.Delivery.Service.AbstractODataService.HandleException(Exception e)
at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass19_0`1.<Execute>b__0()
at Sdl.Web.Delivery.Service.Utils.PerformRetry[T](Func`1 block, Int32 retryCount)
at Sdl.Web.Delivery.Service.Utils.Retry[T](Func`1 block, Int32 retryCount, Boolean locking)
at Sdl.Web.Delivery.Dynamic.DynamicMappingsRetrieverImpl.GetPublicationMapping(String url)
at Tridion.ContentDelivery.DynamicContent.DynamicMappingsRetriever.GetPublicationMapping(String url)
at Sdl.Web.Tridion.CdApiLocalizationResolver.ResolveLocalization(Uri url) in C:\TeamCity\buildAgent\work\531db7af87a3c68e\
.deploy\source code\web application\Sdl.Web.Tridion\CdApiLocalizationResolver.cs:line 66
at DynamicModule.ns.Wrapped_ILocalizationResolver_07bdbb33943c4e17b78d7c0d5a1e643d.
<ResolveLocalization_DelegateImplementation>__0(IMethodInvocation inputs, GetNextInterceptionBehaviorDelegate getNext)

1. Follow the instructions in the hotfix ReadMe to install the fix.

2. Download the following dlls from Package Manager Console 
   Microsoft.OData.Client.dll
   Microsoft.OData.Core.dll
   Microsoft.OData.Edm.dll
   Microsoft.Spatial.dll

Install-Package Microsoft.OData.Core -Version 6.15.0
Install-Package Microsoft.OData.Client -Version 6.15.0

    Note: You can also download the Microsoft DLLs directly from www.nuget.org. Just rename the .nupkg file extension to .zip and extract as a normal zip file.
    It is advisable to use version 6.15 as opposed to a later version as that had been tested successfully.

3. Manually overwrite the assemblies specified in above step in your application (for example, DXA 1.5) with version 6.15.

4. Add the following assembly bindings to web.config:        

<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.OData.Client" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="6.13.0.0" newVersion="6.15.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.OData.Core" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="6.13.0.0" newVersion="6.15.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.OData.Edm" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="6.13.0.0" newVersion="6.15.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Spatial" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="6.13.0.0" newVersion="6.15.0.0" />
      </dependentAssembly>
    </assemblyBinding>