Thank you, that makes sense, I have recently doubled the size of my mining farm, ie now I have two, so am interested to see the longevity of S19s having got rid of faulty S17 just in time, and about to give up on a very trusty late model S9.
From my experience the 19 series are just as bad as 17 series. I have 36 x S19 95t purchased from two different batches (21 + 15) around 2 months apart. So far, 2 x PSU have died and 4 hashboards totally dead, with a 5th that's intermittent. All failed inside the 12 month warranty period (around 9 - 10 months in), however Bitmain refused to take back only the faulty hashboards, so with shipping costs (for sending the whole miners) and downtime I figured I'm better off to just leave the miners running on 2 hashboards. The same applied for the PSU's - I just bought some directly from Bitmain for around 130 USD each if I remember correctly (which is a fraction of the cost to ship a complete miner).
As for 17-series, there is definitely something in placing them horizontal to wake hashboards up. I have no idea why it works, but it does.