A game with so many systems (e.g Fallout, Skyrim) can only work so well. You fix one glitch another takes its place. (That's how coding works) Essentially all the game mechanics at work tend to interfere with the memory allocation, even by the slightest bit. You ask yourself why gta isn't as buggy. It's because Gta has little to no rpg mechanics. ( numbers that can be altered in the slightest manner can throw off even the most complex mechanics. Alter a variable by 0.02 in a system and something will probably conflict with that choice.) Something like Gta may have random generation but in a sense it is within a certain controlled spectrum. (i.e. Helicopters and planes only spawn at airports, dunebuggies and dirt bikes only in Blaine county)