Good news, Proof of Stake appears to have stabilized for now... A theory forwarded to us by Spencer & his co-workers is that the wallet in question accumulated a LOT of stake weight resulting in PoS domination & has now run out of stake age. This may be addressed in a future wallet update.
Stake weight... I thought that wasn't a thing in PoS 3.0...
Correct, hence the unsolved mystery. I'm personally just happy it does not look like an exploit.
We will either get Spencer to delve into it when possible, or if he remains unavailable in the long term, find a full time developer to join team $troll