Multipart file upload with httpd proxy and SSL -> prefetch request body failed

I'm currently facing a problem where i can't find a solution for.

I'm developing a WebClient application with angular where i create a multipart/form-data with boundaries request and this request i wanna post to the server. My backend is a apache 2.4.6 as a reverse proxy and a tomcat 7.0.76. For the OS I'm using Centos 7.4.1708. I'm also using TLS1.2.

So i wrote a upload function for uploading multiple files. I append the files to a formdata object:

    let uploadFiles: FileList = this.inputElement.nativeElement.files;
    let formData = new FormData();
    for (let i = 0; i < uploadFiles.length; i++) {
       let fileName = uploadFiles[i].name;
       let file = uploadFiles[i] as Blob;
       formData.append('uploadFile', file, fileName);
    }

After i did that, i append additional informations to the form data:

formData.append('request', JSON.stringify(this.requestUploadFileRaw));

So, when i look into the chrome developer tools the request and everything looks fine. But only when I'm doing this with a very small file. I played around a bit and the max filesize i got was 292 bytes.

All this happens when i add TLS1.2 and the apache proxy config.

When i try it on my dev-environment without tls1.2 and without a reverse-proxy everything works fine.

The error i get in the apache log is:

[proxy_http:error] [pid 1381] (70008)Partial results are valid but processing is incomplete: [client 127.0.0.1:36828] AH01095: prefetch request body failed to 127.0.0.1:8080 (127.0.0.1) from 127.0.0.1 ()

The request doesn't get redirected to tomcat at all. And i can't find a solution for this on the internet. Am I missing something? Because it is working with a very small files but not with bigger files.

Thanks for your help!