No php output when using Xdebug DBGp proxy - proxy

Question

When using Xdebug directly from VSCode using one of two PHP extension (xdebug.php-debug, devsense.phptools-vscode) for debugging everything works as expected. But I have a shared environment where an Apache/PHP/Xdebug setup/instance is to be used by multiple developers.
With both extension everything works well when being used directly receiving the Xdebug connection. I have a breakpoint at the last line of code and although the whole HTML content was completely sent by PHP the browser it is still waiting to do anything - although ob_end_flush() (output buffering) was already called. Stepping over the last line of code the HTML content arrives at the browser. The Xdebug log is finishing in the same way.
[Step Debug] -> <response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="https://xdebug.org/dbgp/xdebug" command="run" transaction_id="14" status="stopping" reason="ok"></response>
...
[Step Debug] -> <response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="https://xdebug.org/dbgp/xdebug" command="stop" transaction_id="22" status="stopped" reason="ok"></response>
When I now set this up using DBGp proxy the two PHP extension behave different. One is blocking the HTML output forever for all request been started and if I kill the apache processes I get a proxy log
21:01:28.652 [warn] [server] Handler response error: Error reading response: Error reading length: EOF
21:01:28.652 [info] [server] Closing server connection from 127.0.0.1:60104
21:01:28.653 [warn] [server] Handler response error: Error reading response: Error reading length: EOF
21:01:28.653 [info] [server] Closing server connection from 127.0.0.1:35422
21:01:28.653 [warn] [server] Handler response error: Error reading response: Error reading length: EOF
21:01:28.653 [info] [server] Closing server connection from 127.0.0.1:43594
21:01:28.653 [warn] [server] Handler response error: Error reading response: Error reading length: EOF
21:01:28.653 [info] [server] Closing server connection from 127.0.0.1:56398
21:01:28.659 [warn] [server] Handler response error: Error reading response: Error reading length: EOF
21:01:28.659 [info] [server] Closing server connection from 127.0.0.1:40030
while the other is delivering the HTML output and says in the proxy log the same moment
22:02:02.316 [warn] [server] Handler response error: Error reading response: Error reading length: EOF
22:02:02.317 [info] [server] Closing server connection from 127.0.0.1:33160
In both cases the Xdebug log says the same: status stopped, reason ok.
So I wonder whether the way the request seems to completely end in both cases reading an EOF and closing the server connection is really a warning because it's unexpected or whether this is the normal behaviour. And then of course it's an issue of the one PHP extension seeming not to tell the proxy and server they can end their connection (I assume this is the client's job which here is the proxy).
I checked all configuration options from Xdebug, the VSCode PHP extension and DBGp proxy to increase logging but I could not find out more than what I have described above. I tried setting the connection either via the VSCode extension or manually issuing echo -e "proxyinit -p 39001 -k jni-vscode -m 1\0" | nc 127.0.0.1 9001 with no success. The EOF warning stays and for the devsense.phptools-vscode plugin there is no php output to the browser. If anyone has a clue why I would appreciate a hint.
Thanks,
Jürgen
PS: Killing dbgpProxy makes apache deliver all the content with access_log entry showing it took 3064 seconds to fulfill the request.