DocKey is invalid error message

I have installed the docker image for nextcloud and collabora. Collobora is configured behind apache reverse proxy.

Now i get an 400 Bad request when connection to the websocket and the log states:

#20 Exception while processing incoming request: [GET /lool/…]: DocKey [/apps/richdocuments/wopi/files/666_oc6tfxlvkps7] is invalid.| wsd/LOOLWSD.cpp:2156=/ws HTTP/1.1

Can you give me any clues what is causing this error ? What is happening in the code when validating the DocKey ?

Thanks for any pointers!

The anwser was simple, but hard to find. In the websocket proxy config, ProxyPass instead of the correct ProxyPassMatch was used. So it didn’t process the RegEx