In-game shop bug; "undoing" a purchase also resets health/mana that has been regenerated.

Sorry if this is a repost, scrolled through a few pages worth and didn't see it listed:

When I go back to base to shop, if I purchase an item while regaining health and mana and then decide to 'undo' my item purchase, it not only will undo the purchase, but also take away the health and mana I've regenerated since purchasing said item.