I recently took a trade buying 40 carriages and the sum total of carriages after the trade was less than it should be...
Before Trade: 5 carriages in stores, carpenter mid cycle
Trade: Bought 40 carriages
After Trade: 35 carriages in stores
Obviously I should have had 45 carriages after the trade, so I presume the math is wrong somewhere, a minus rather than a plus.
Note: The trade appeared in the history correctly, showed purchase of 40 carriages, stores now only show 35 (and the guild quest says 35/40 toward completion). I have tried a refresh and checked the various panels numerous times. I have already sent a support ticket, just adding it here in case other people have found the same problem.