Hi Shaun,
It worth a try to use supported combination of the software published in MOFED User Manual and start with using the same HCA and FW level. Using unsupported OS and mixing CX-2 and CX-3 can lead to unexpected behavior..
Use the link bellow in order to download release notes.
http://www.mellanox.com/related-docs/prod_software/Mellanox_OFED_Linux_Release_Notes_3_1-1_0_3.pdf