On the OP's videos: The spiderweb thing looks to be a bug, and one that I have yet to read about anywhere online. It almost seems like it is set to be indestructible unless some other trigger fires off. The map marker issue is, however, not due to the game, but due to the map being in 3D and you placing a marker on a spot where the cave is not. Next time try rotating and scrolling the map to see exactly where the cave is and placing a better marker. Really, that is a frivolous complaint and a real stretch in calling something like that a bug.
After 250 hours and 6 characters here are the bugs I have witnessed:
Excessive crashing in Bonechill Passage.
A puzzle in Raldbthar being reset in an unusable state.
Companions quest sharing the location of a Helm quest and not triggering properly.
Some guy getting stuck waist deep in the terrain at Whiterun stables, followed by more of him being spawned in the same location (quite hilarious actually).
One cave where I found a hole in the geometry and was able to go into the terrain and just walk out of a wall*. Sadly, I forgot to write down the name of that cave.

* Actually, I was quite surprised by this, as most games have geometry as a 2-way blocker, meaning once you get on the other side of the geometry you cannot go back through. The fun part was sneaking out of the cave wall behind an enemy for an execution.