you ruled out the MCP2515. What about the display? do you get the same issue if the display is not connected?
Do you get issues with the GSM module? does it stay connected when you have problems with the GPS?
The only thing i can think off is an unstable power supply.. or not enough power. But 2.5A should be enough.
Does the problem follow the power supply around?
Mark --OzzMaker.com --
