Stuck in headphone mode after replacing lightning port

Hi. After having an issue with my iPhone 5s not charging properly, I purchased a replacement lighting connector part of the phone and set about replacing it. After re-assembling the phone, everything works fine, apart from the phone believing that there are headphones plugged into the headphone port.

This means that I cannot hear on calls unless I put it into loudspeaker mode. If I plug headphones in, I am able to hear sounds via them. I have also checked that the headphone port is clean.

What could be causing this issue potentially? I have opened it up again and checked all of the connectors were as I found them and that everything is plugged in.