Using MDM installed client certificate in Safari

Hello,

We are building an MDM solution. Using this solution, I install three certificates on the device. One of them is the certificate I want to use for client authentication in Safari. I can see all three certificates in Settings->General->Device Management->Name of Mangement->More Details under certificates. The devices are using this certificate as the client certificate for communication with the MDM server, this is working without problems. Now I want to use a Webclip that links to a website with client authentication. When I enter the URL I want to connect in safari, the connection does not work. Safari does not ask me which certificate to use, it just sends an empty certificate (tested with wireshark-trace). As expected, server then sends a critical alert. However, it worked some times on two of our test-devices but I can't find any system when it is working. It is not working almost every time. I am using different devices (iPhone and iPad) with different versions of iOS (from 7 to 10). I am connecting exactly the same server:port as the MDM server, so the certificate request from the server is the same for MDM and the request I want to make with Safari.

Thanks in advance