I have my theory about the most likely sequence of events that lead to this, but I would rather not share it, because I don’t know what really happened.
Statistically this type of issues often occurs due to the lack of communication between parties involved in the product development. Datasheet for RS-485 driver states that:
Whoever made decision not to add TVS devices to V5 brains apparently assumed that it is consumer grade equipment that is not exposed to industrial level hazards.
However, there was plenty of anecdotal evidence that ESD is quite frequent phenomenon on the VRC fields.
Even if Cortex IME unreliability, long suspected to be caused by ESD, was never resolved and mostly forgotten, ESD was brought up again between January and April earlier this year while discussing VexNet resets. VEX engineers might have concluded that VexNet resets were due to the bad competition ports abused by the students, but the ESD theory was still front and center for weeks on various online platforms.
Back then @Paul Copioli said that they have an ESD gun in the lab.
Did anyone try to fire it at a realistic V5 robot as it was driving around the field interacting with the game objects?
Was there enough time to make another revision to V5’s PCB that would include ESD protection (that could cost as little as $2 per V5 brain)?
In any case, rather than finding whom to blame, it is more important to see what could be done now to avoid killing even more V5 ports.
Anti-static spray is a very good first step to address the highest risk environments - on the competition fields but, I feel, another line of defense would be warranted. We will try to run some experiments locally to test effectiveness of various protection methods on a few robots that are already partially damaged and need to be RMA’d anyways.