Since you have checked everything as described, @Lafonte could be right in his statement.
It is conceivable that this is the cause of the error.
Hifiman is known to have a very poor quality check.
Even with larger models there are always complaints.
If you have another pair of headphones and no problems have occurred in this regard, that would definitely be the most obvious thing to do.
Send the Hifiman back with a note saying you suspect a short circuit that destroyed the equipment.
It is conceivable that if there was a production error, a batch of Sundara is affected.
Hifiman must investigate whether this is due to the headphones or the headphone cable and whether this has occurred once or several times.
As you said, you have a wooden desk and a tile floor, which alone is not enough to cause ESD. Since you also use mats and wristbands, this should definitely be a thing of the past.