Unable to do "big" POST request with Apache2 and ProxyPass

Question

I have an apache2 server, configured with proxypass to access a servlet which runs under Jetty. Now I have a problem with large POST request (600KB). The configuration is as follows:

<Location /myurl>
    ProxyPass http://127.0.0.1:8080/myservlet retry=3
    ProxyPassReverse http://127.0.0.1:8080/myservlet
</Location>

I am uploading a base64 encoded image to my servlet with a POST request. When I do it directly to Jetty on port 8080, everything works fine.

When I am using Apache on port 80 with Proxypass as configured above, only about 106085 byte will be forwarded to jetty, thus the image is uploaded only partly.

When I am testing with a smaller image (70 KB) everything works fine.

I already tested with a high

LimitRequestBody

value in the Apache settings. It didn't work. Or with no LimitRequestBody, didn't work either.

Also, I tested with the

SetEnv proxy-sendcl

command for proxy pass, but that did not work either. (Also, the request is not chunked).

Please help, where is the hidden setting I have to change, so mod_proxy forwards the whole request to Jetty?

Thank you!!!