Invalid content length error using HAProxy

Hello everybody,
in an app we are using the TIWCGJQFileUpload component and in our lan the upload works perfectly.
If we use the app via internet in combination with a (reverse) haproxy, the error message
Invalid content length
always appears immediately when the upload is started
Do I have to make any special adjustments in IW servercontroller or in the component to solve the problem?
Complete: AParams: ajaxevent=JQFileUploadOptions.OnComplete
callback=FILEUPLOAD.DoAjaxRequest
ComponentName=FileUpload
FILEUPLOAD_StoredFiles=[]
in an app we are using the TIWCGJQFileUpload component and in our lan the upload works perfectly.
If we use the app via internet in combination with a (reverse) haproxy, the error message
Invalid content length
always appears immediately when the upload is started
Do I have to make any special adjustments in IW servercontroller or in the component to solve the problem?
Complete: AParams: ajaxevent=JQFileUploadOptions.OnComplete
callback=FILEUPLOAD.DoAjaxRequest
ComponentName=FileUpload
FILEUPLOAD_StoredFiles=[]