A lot of requests with large body content size cause the server port drops

Hi, I'm a developer on the project Galeb Router .
The Galeb project implements a layer 7 load balancer based on Undertow 2.0.20.

When we test the router with more than 4,000 concurrent users and perform a request with 175 KB body content size the server port drops.
When we execute same load test with http method GET the server port not drops.

Is there any special treatment we can give for PUT / POST requests with large request body?

Implementation of ProxyClient is this: https://github.com/galeb/galeb/blob/master/router/src/main/java/io/galeb/router/client/ExtendedLoadBalancingProxyClient.java