I don't have the same bugs as you lol
Currently, I'm going to get the quest to save the merchant.
But when I enter the guild, I can't move. The background animations move but that's it.
And the scene of Rebecca explaining the quest doesn't start. But the bug doesn't stop there.
I go to the Labyrinth Forest. I can reach the bandit camp to the south. I can distract the bandits. I can explore the basement and even save the merchant. I can return to the city with the merchant and choose one of the three rewards.
So, you're going to tell me, everything's fine after all... But actually, no.
When I go to the guild, the merchant's event starts, and I get the quest... even though I've just saved him.
And of course, since I've already saved him, I can't save him a second time.
I can go back. Distract them again, go to the basement again and get him out of his cell again... but that's it, I can't bring him back to town, and therefore I can't finish the quest.