Saving Case Update Thread refuses due to unsafe header

I’ve been trying to update some cases on the Case Update Thread section in detailview. However no new updates are being saved and Google Chrome console throws the following two errors
Refused to set unsafe header “Content-length”
Refused to set unsafe header “Connection”

Can anyone help me out here?

I found the issue. Thanks a lot pgr for the detailed guide at https://github.com/salesagility/SuiteCRM/issues/2237