Just started playing for the first time in a few years. I downloaded the latest version of SWATH and after a few minutes' trading, went to buy some more cargo holds. For whatever reason, it didn't update how many holds I have - I'm at 25 holds, the game thinks I have 10, and does pair trades accordingly.

Anyone know how I can fix?

SWATH doesn't update your ship when you buy stuff at StarDock, only when you hit "I" or "/," so it is a good habit to hit "/" whenever you leave the StarDock (or a Class 0 port) after buying upgrades.

Have you registered?

I stand corrected!

Under SWATH's preferences, [the green circuit board icon, [alt][enter], or under the Edit dropdown] on the first tab, there is an "Update info when leaving SD" checkbox, but I don't know if it works consistently.
I updated my keepalive script to hit / when I leave StarDock--sometimes both SWATH and my keepalive script check quick stats.