Error when accessing DLL on specific server

I am trying to read the Version from a DLL using Powershell using this code:

Add-Type -Path "\\myuncpath\my.dll"
$version =  [MyProd.MyVersion]::CurrentProductVersion + '.'  + [MyProd.MyVersion]::CurrentBuild

It works on all of my server except one. On this one I am getting the following error:

Add-Type : Die Datei oder Assembly "file://\\myuncpath\my.dll" oder eine Abhängigkeit 
davon wurde nicht gefunden. Der Vorgang wird nicht unterstützt. (Ausnahme von HRESULT: 0x80131515)
In Zeile:1 Zeichen:1
+ Add-Type -Path "\\myuncpath\my.dll"     
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [Add-Type], FileLoadException
        + FullyQualifiedErrorId : System.IO.FileLoadException,Microsoft.PowerShell.Commands.AddTypeCommand

Sorry for it being German but I guess sole the stack trace will help out as well.

I was already comparing the config files on the different servers but there was no difference. I am not knowing of different settings on the server but I guess there has to be one.

I already tried to use Unblock-File, set <loadFromRemoteSources enabled="true" /> in the config and also Set-ExecutionPolicy RemoteSigned. However nothing worked.

It is should be important to know, that if I copy the file to my local machine and change the name of the file I can access it.

I hope I am missing out onto something dumb. Thanks in advance for your help.