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.
Out of curiosity, what is the air temperature where they are running? I've found that unless the ambient is less than 30C the miners will never finish their tuning mode and as a result will run slower.
As for Pango support failing - surprised to hear it! While I've never had a problem with my M10's that I got from them it is rather distressing to hear that the company is slacking off. At least in the past, they had pretty decent service.