i played nwn2 with all patches and i still couldn't finish the original campaign because of bugs. for some bugs i googled the problem and fixed it with the console etc but at the end of the game when i reached the last map i lost my silver sword - a quest item. and a good weapon from that female druid Elanee AND a magic bag which contained all the crafting items i had. so i quit and watched the game ending on youtube.
as for nwn1 i finished OC and the 2 expansions. i think there was only 1 gamebreaking bug - if i saved near that boat in hordes of underdark, when i load the game, the frame rate goes like 1 per second or even less. it's impossible to even leave the map. and then there's another bug if you try to be a pale master from wizard or sorcerer because your caster level doesn't rise even if you gain pale master levels. so far nwn1 was decent but from all the 3rd party mods i tried i only finished 1 - wyvern crown of cormyr. but even that mod was bugged too. first thing i noticed, there were items with invisible textures - they looked normal if i wore an armor etc but when i looked at the item in inventory it looked transparent: parts of it or even the whole item. and later in the game you could talk to your companions to make them gain infinite levels '> i tried blackguard, infinite dungeons, tortured hearts and they're all bugged?
as for me i have nwn1 1.69 GOG version with cep 2.4a installed. can you recommend me some good mods which i can actually finish? without bugs?