I was able to reproduce this bug the following way:
Go to Buy/Sell Screen
Increase the quantity of an item, decrease the quantity of the item
The amount added back to your funds appears to be 90% when you decrease the quantity. It seems to me that if there is going to be a "resale" penalty, that should be applied after the actual purchase takes place. Otherwise an errant mouseclick could cost a play thousands of credits.
I searched the forum, docs, and FAQ and couldn't find that this behavior was documented or had already been reported as a bug. I'm a first time poster here so please educated me if there is a resource I have missed.
Aside from that, thanks for the hard work. I'm a software developer at my job (mostly web stuff) and when I get some free time, I'd like to be able to contribute to the effort and maybe fix a few bugs myself.
--- ADDENDUM ---
I originally did with with the AA51 Missile Launcher, but replicated it with every other piece of equipment I could buy/sell as well. I'm thinking the 90% rate for selling is very purposeful, but as I mentioned earlier, that seems a little uncool considering that could cost a few grand for a misclick. I'm not too sure about the whole buying/selling interface in general... seems it would be more functional in an invoice-type format where the player could see everything they were purchasing, etc. I know that deviates significantly from the original game, but might be a good improvement.
Thanks,
m. meitbual