AI constantly plays Trade but doesn't trash anything

[holeypants]

In a 3-player game, both Lord Rattington and Revenge Witch spent turns 7-22 doing nothing but this:

Turn 18 - Revenge Witch
R plays an Alchemist.
R draws a card.
R gets +1 Action.
R plays a Chapel.
R plays a Silver. (+$2)
R plays a Goat. (+$1)
R plays a Potion.
R plays a Silver. (+$2)
R buys a Trade.
R trashes nothing.
R topdecks an Alchemist.
R shuffles their deck.
R draws 5 cards.

Finally in turn 23 they switched to buying Duchies.

The cards available were:

Chapel
Embargo
Pixie
Menagerie
Alchemist
Moneylender
Nomad Camp
Mystic
Rebuild
Harem
Triumph
Trade

The AIs' final inventories were:

Revenge Witch:
2 Silvers, 6 Estates, 5 Duchies, a Chapel, 2 Alchemists, a Potion and a Goat

Lord Rattington:
2 Silvers, 6 Estates, 5 Duchies, a Chapel, 2 Alchemists, a Potion and a Goat