I found a bug with ch10 on Eirikas route. (Revolt at Carcino)
You can recruit Gerik, Innes and Tethys but Gerik disappears from your party when you return to the world map, after the save screen.
I tried replaying it without recruiting Tethys and it still happened.
Also when a random encounter is on that tile on the world map it reloads chapter 10 with the levels i gave gerik instead of doing the skirmish.
Not sure if its relevant but Gerik was randomized to a fighter.