You have to collapse ceiling after you enter the tunnel. I think it may a bug related with protective sign (anyway in my case). You are not supposed to survive falling rocks. Before you enter the big chamber there’s a body on the left with yellow meteorite if you’ve missed it.
Please remember to put spoiler in the title when giving away game spoilers or asking a question that would need spoilers in its answer. I'll do it this time but future threads that do not put spoiler in the title when required may end up being deleted.
