While repeatedly hitting the sector mine limit and reloading mine launchers in an in-sector trident, I encountered one of the two mine launchers not reloading properly after multiple tries (i.e. it was jammed). Warping to a station and reloading there didn't work either.
[Edit: After re-logging, my mine launcher appeared to be reloaded.]

Also the ammo count is not always right after reloading (if it works), when the sector limit is hit. So it might display, say 2 and 1 mines in both launchers. When one lays new mines when others timed out or were destroyed, the ammo count sometimes (always?) jumps back to the correct count.

Thanks for the report!