(I'll keep updating this post as i play the game)
So guys i'm gonna address this issue since i love the dragon age series and i play it again from time to time and this error was ruining my experience so hope this helps u all.
I'm not computer expert but i had problems playing the game in very high settings, i read a lot of posts and i kind of found a partial solution to it.
For some reason i have the problem only in the Denerim Market so try this tips for now:
1. Use very high settings everywhere except in Denerim Market for some reason it makes the game crash.
2. Do not use the quick save option. The issue with this is that we sell equipment to Bodahn to upgrade it, but since i'm impatient i used the F5 option and as soon as i checked the store and saw it didn't have the level i wanted i exited quickly and pressed F9 to check again. Repeating the process i noticed the game started to get laggy after i did this, so i started saving the game normally (using the the save game option) and deleting the old save and this fixed the laggy issue, for the moment i'm not overwriting the save cuz i don't want my game to crash again (doing this only to be cautious don't know if this affects the game or not).
I've used this tips and game has been running fine for me. So to summarise, keep very high settings everywhere and switch to medium whenever you're entering Denerim Market and use different save slots.
Let me know if this worked for u and sorry for my grammar, English is not my first language.
