I thought I would briefly summarize the sorry history of my experience with the quality control of the HiFiMan HE1000se. Sonically they have been outstanding, a little bright, but this has been easily compensated by a little EQ. The problems are in the manufacturing quality control.
My first HEKse was back in 2019. It almost immediately developed an intermittent right channel. It was the connector. HiFiMan replaced it, and it worked correctly for about 2 years. Recently the intermittent connection problem again came up, in this replacement pair, this time in the left channel. The problem was even worse, with no sound most of the time. So HiFiMan replaced this pair.
But this new replacement pair had another kind of defect - both headband clamps were loose, so that the headphones would slip upward or downward out of their setting whenever I took the headphones off or on, requiring frequent resetting the clamps.
So now my new just replaced HE1000se's are on their way back to HiFiMan for yet another replacement. At least they have been courteous and prompt in granting and sending replacements. I don't know if I would have started the whole process if I had known how many defects their product would have.