@kevink all good! …You never know until you try haha
We are using 2 x 4S 18000 mAh batteries in parallel (Sorry I mis-typed before!), the larger version that is available from the Blue Robotics website.
As per the assembly instructions, in addition to the pixhawk power module, I 'm using a 3A 5V BEC to power the pixhawk through the servo rails (and i guess there may be a bit of current drawn of that USB connection).
Have been trying to debug this issue all day and have come to the conclusion that there may be a ground loop happening due to the use of multiple power supplies.I’m thinking this because on both occasions, the two ground wires on that six wire pixhawk ribbon cable were the first to fry. The only issue with this theory is that I’ve never seen this before during all normal operation, and, no one on this forum has encountered the same issue!!
Thanks for all the help so far