I've just sent off for a board revision to be made, in which a swap between MCP2515 CAN controller packages from TSSOP to QFN was made, however - just quickly looking through the revised board again, I've just noticed no connected between the exposed pad of the QFN and ground.
Panicking, I looked at the datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/21801G.pdf
Unlike most devices, it does not specify a requirement to connect the exposed pad to ground, it just says see table 1-1, in which there is no mention of the thermal pad.
What would be everybodies opinion? No explicit declaration of said requirement = not required?