Well the s9. had a lot of bad batches say 4 to 11 way back say. sept 2016.
Also. I am willing to bet that. a ton of s17 gear was burnt due to too much over clock.
You are absolutely correct !!!They were shipped overclocked straight out from Bitmain. Among the several tests I have been performing the last 10 months with those S17 series I have discovered that they are overclocked for several reasons but I am going to mention a couple of them.
1- The HW error factor is unusually higher than average, if there are no problems with the internet connection the next cause for this to happen is aggressive overclocking
2- The working temperature factor of the miner is too high even on controlled environment ( 23 degrees celsius ) or winter time, plus the fan speed is also too high 90% of the time.