MOVING THIS POST to a more appropriate forum.

I am playing LOTRO on my imac 27" with a new character and noticed in some of the instances in Southern Barrow-Downs
that some of the rooms are clipped/missing until I move several steps forward into the room, then everything appears.
If I step back, the room clips/disappears again.

I am running on a low or medium graphics setting, because when I run on
high or ultra graphics mode, the game crashes a lot when I use my 95 character in Rohan.

Is there a specific setting/adjustment I should be changing to compensate for this clipping ?