You should start the game with a few common chain gun turrets and mining lasers.

What mods are you running?

Definitely a mod issue. Check which ones do anything with weapons. Double check that they all say they support the version you’re playing on (if you’re on beta, check to see if they’ve been updated since beta released at the start of August). Disable mods a few at a time and check see if the equipment docks are selling again until you find the culprit.