Ok so the unpredictable pricing is "by design"? I tried to dip my toes into trading the other night, and thought I had spotted an opportunity for selling some machinery in another system. But when I arrived 5 minutes later, the whole thing was a loss. I spend like an hour trying to get rid of my cargo at profit, but wasn't possible. I have given up on trading as fast as I tried to learn it.
Ive had that, you learn to stay away from specific commodities without a backup market or like you say you get stuck with some random stuff. Don't give up, try a bit further out in the bubble, less traffic. Look for certain states and sytstems. Industrial in boom near Agri in Outbreak is good, Basic Meds one way, Mineral Oil the other if youre lucky or just beer, theres always beer....and tea

Found one the other day was making 4K per ton on the meds and 1K per ton on the Oil back, both stations less than 100ls away from main star. Nearby was a Military base buying Military Fabrics for 11K per ton profit but that was 180Kls so only did that run twice. Prices held for over 2 days. OK its not mining but the routes are there. Otherwise just buy cheapest regular good at best below Galactic Average then even if the target station has filled up you can still get rid of it easily such as Food, Beer, Meds, performance enhancers, lots of minerals eg Platinum, Beryllium.
I rarely fly empty and look to make min 500 preferably 1K+ per ton against Galactic Average then can usually get more or can sell below average just to get rid of the stuff and still make a small profit even if just to make room for a better trade.
Market on RHS has 2-3 systems/stations buying and selling the commodity so you can have a backup. Go to sell market if not showing your commodity.
...As far as not suggesting what you've already tried... anyone that has even tangential exposure to IT and troubleshooting with the public knows the folly in assuming the monitor is powered on when user reports a video card is not working. That was yesterday.
OK I now forgive all the 'stupid' questions I have ever suffered from I.T. Now I understand.