Dell XPS 13 Developer Edition - SD card reader not working

I recently bought the Dell XPS 13 Developer Edition (9350). A month or so into using it the SD card reader suddenly stopped working. The output of lspci (attached) shows that the card reader isn't even being recognised. I have spoken with technical support over twitter and they referred me to this link which didn't solve the issue. I have also updated the BIOS.

Today (1st December) I have had an engineer on site to address the problem. I explained that the problem has persisted on Ubuntu 16.04 and 16.10.

They replaced the card reader but still the problem exists. I'm awaiting a call from the technicians but in the meantime does anyone have any insight into what might be causing this?