When I loaded up my game today, I found my weapon skill (Thrust) missing. Played for a while and got another weapon, but it didn't seem to load up any weapon skills whenI equiped it.
Startaed new game to check - seems like after I unequip a weapon and reequip it, or drag it to another slot, the weapon skill just disappears.

*Edit*

Right, so, do *not* install the game through GOG Galaxy. For whatever reason, the version Galaxy installs is older than the one you get from the installer in your library. The Galaxy install does not have the bugfix for this issue, the installer from the site apparently does.

Original post:

It's a known bug. It was supposedly fixed on Steam almost immediately, but so far there's been no sign of a patch for the GoG version whatsoever :/

Your solution checks out. I thought it weird that galaxy marks gog-3 as the latest version when the offline installer is marked as gog-4. Joys of fresh games huh?

EDIT: If you want to run it via galaxy anyway just install from the offline installer as mentioned above,let galaxy detect it then stop the update and disable autoupdates.Failing to do so will rollback your version to gog-3 aka the one containing the disappearing skill bug. Hope all that helps!

Yesterday was GOG-4, now it's showing as GOG-3. Have to patch it now.
Have to reinstall it :(

I'm hoping they fix this tomorrow when they get back to work, as I use Galaxy and like doing so... I'm not touching the game until GOG Galaxy updates it to GOG-4.

It is fixed now. Rejoice !