AH00524: Handler for (null) returned invalid result code 70008

I have a WHM/cPanel server that I can only post to a PHP script with a byte array length of 12249. Anything bigger is not received. On another server that I rent I receive all 299000 bytes. In the Apache error_log every time I post with a big array of bytes, I get this: [Fri Oct 12 11:14:18.970213 2018] [core:error] [pid 30852:tid 140053705647872] [client (MY_IP):50402] AH00524: Handler for (null) returned invalid result code 70008 I have the following settings set: Max Request Workers: 150 PHP: post_max_size: 5000M memory_limit: 1000M max_input_vars: 5000 max_input_time: -1 max_execution_time: 90