Download and stream not working via VPN

When trying to download (network tab in the bottom of the screen -> download) or stream (network tab -> stream) a file from a local server in my home network via VPN (IPSec to FritzBox), it unfortunately doesn't work.

I immediately get the error message "Download fehlgeschlagen libvlc failure" (in German; meaning "Download failed").

The download/stream works fine as soon as I am in the local Wifi. Accessing the file in the browser also works and can stream the video, so it is accessible through VPN.

If I can provide any more information, please let me know.

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