I'll just mention that I put 6 Pangolin M20 units into service this January 2020, rated 45TH/s each. They all ran at that speed for many weeks, then, one by one over the next few months, most had dropped to 30-35TH/s and would not go faster.

Finally, over the period May 28 to July 23, all 6 units eventually died. They no longer boot up. The last one died a few days ago. Early on I sent emails to PangolinMiner requesting technical support/service but still haven't heard anything after at least a month. I had a couple dozen Bitmain S9's before this, but they had their own hardware issues over time so I gave Pangolin a try. Unfortunately the experience has been even worse.