After an eternity of never knowing why once in a blue moon people would end up with negative mana on their Towers I finally figured out how to reproduce it.
Turns out when a Tower had a Timed Buff applied to it and then that Tower was moved it would remove the Buff's stats from the Tower on move and then again when the buff's natural duration finished.
So for the two people that had negative mana regen what was happening was a double-removal of the Generator's buff which gave them -300% mana regen permanently.
I fixed the bug but then realized there's no harm to letting Towers carry their timed buffs with them after moving so I have allowed that as well. You could consider it a tiny buff to the Cactus I guess.
Patch Notes:
- Fixed Timed Buffs removing their stats from Towers twice if the Tower was moved while they were active.
- Timed Buffs from other Towers no longer get removed when you move the Tower being buffed.