Problem with reverse proxy and SSL configuration on Windows

[Ieldra]

I am trying to set up an oTree Server on a Windows virtual machine with an SSL and reverse proxy configuration. I have the problem that some functions result in a hang and an internal 404 message. I have configured websockets according to an example I got from a colleague, and I can't see what might be wrong. Here are the relevant file excerpts:

httpd-proxy.conf:
ProxyRequests Off
SSLProxyEngine On

#ProxyTimeout 600

ProxyPreserveHost On
ProxyPass / http://localhost:8000/
ProxyPassReverse / http://localhost:8000/

RewriteEngine On
RewriteCond %{HTTP:Connection} Upgrade [NC]
RewriteCond %{HTTP:Upgrade} websocket [NC]
RewriteRule /(.*) wss://localhost:8000/$1 [P,L]

ServerSignature Off

<Proxy *>
    Require all granted
    Options none
</Proxy>

access.log:
[03/Mar/2021:11:09:42 +0100] "GET /no_op/ HTTP/1.1" 404 77
[03/Mar/2021:11:10:35 +0100] "GET /demo/ HTTP/1.1" 200 4841
[03/Mar/2021:11:10:38 +0100] "GET /demo/cardio/ HTTP/1.1" 200 3576
[03/Mar/2021:11:10:38 +0100] "GET /static/bootstrap4/css/bootstrap.min.416bb9e03b22.css HTTP/1.1" 200 20487
[03/Mar/2021:11:10:44 +0100] "GET /create_demo_session/ HTTP/1.1" 404 77

ssl_request.log:
[03/Mar/2021:11:10:35 +0100]  TLSv1.3 TLS_AES_256_GCM_SHA384 "GET /demo/ HTTP/1.1" 4841
[03/Mar/2021:11:10:38 +0100]  TLSv1.3 TLS_AES_256_GCM_SHA384 "GET /demo/cardio/ HTTP/1.1" 3576
[03/Mar/2021:11:10:38 +0100]  TLSv1.3 TLS_AES_256_GCM_SHA384 "GET /static/bootstrap4/css/bootstrap.min.416bb9e03b22.css HTTP/1.1" 20487
[03/Mar/2021:11:10:44 +0100]  TLSv1.3 TLS_AES_256_GCM_SHA384 "GET /create_demo_session/ HTTP/1.1" 77
[03/Mar/2021:11:11:46 +0100]  TLSv1.3 TLS_AES_256_GCM_SHA384 "GET /no_op/ HTTP/1.1" 77

I'd appreciate any help. It looks like the websockets setup isn't working correctly. I have tried to replace "localhost" with "127.0.0.1" but that didn't help.