Either tether is trading at a discount due to liquidity issues like a closed-end fund or due to real credit issues (fraud).
If they are selling because they can't access the normal withdrawal mechanism (e.g. US customers or people in a rush relative to processing delays) then it is the former. If they are speculatively shorting it is more likely the latter.
It could be both: people who can't do normal withdrawal and think there is at least 2% chance of fraud.
I don't have a position here and no axe to grind, but parting from your auditors is in many cases a significant red flag.