I was going to report this as a bug as well, but I question the logic over on BGG, which says:
It depends on what they say.
Carpenter: "On your turn you may buy 1 wood for 2 silver"
This ability says you can buy ONE wood. It does not say you can buy lots of wood for 2 silver each. Therefore you my only use it once per turn.
Brett "Red" Gilbert: "Pay 2 silver: Upgrade a wagon OR remove a damage token"
This ability is is not limited to one use per turn, so you can use it as much as you like each turn
You could use the same logic to Red. It says Pay 2 silver, not pay 4 or 6 or 8. It also says upgrade A wagon and remove A damage token. I don't know what the developers intended, seems likely that it should be once per turn but the wording certainly doesn't help.