You can do that for testing purposes, but don't play on with a save game after that point. If you disable a mod, everything it added to the game will be lost once you saved your game without that mod. This may also break quests from mods, reset companions and leave leftover scripts in your savegame, that can cause further issues. If something doesn't work the way it should in a modded game, you should always try to find the cause of that issue. How to go about this: Do what WastelandAssassin suggested: Start with a new character, get to Riften and the TG quests as soon as posiible. Now systematically disable mods (10 at a time or so), until you're able to start "loud and clear". Now re-enable the mods you disabled last again one by one, until the problem occurs again. This way you can find the "culprit". You can then try to make a "clean save" without that one single mod. Google how to make a "clean save" if you need to - there are a lot of tutorials / guides on this. Sounds as a reasonable suggestion. So, I start a new game with all mods activated and and after I got to Riften, attempt to complete the quest, disabling the most possible mods, until I get a result, is that correct? After I find the culprit, disable if it is a simple mod and do a clean save. Disabling the mods in a new game won't have any undesirable effects on my main character saved games, right?