5V Regulator causing component damage
Components usually die from overvotlage, when the voltage gets too high for the absolute maximum ratings section. 

I'll bet this is the culprit of the circuit problems:


  It got me confused at this point. Im also driving a 2 channel relay
  board from the DC-DCs output.


Relays without a flyback diode can cause an overvoltage condition momentarily, make sure the relays have a flyback diode. 

Check the votlage rails with an oscillosope while operating the relays to make sure the voltage does not exceed 5.2 (or whatever the max voltage is for all parts tied to that rail. 

Make sure you fuse the input to the DC DC converter