Siddgeir - 'Kill the Bandit Leader' quest bugged, can't receive reward and complete quest
Solution 1:
I solved it by following this guide: http://news.softpedia.com/news/How-to-Use-the-Skyim-Console-to-Get-Past-Broken-Quests-on-the-PC-242822.shtml. Here is what I did:
Open console, then type ShowQuestTargets. Use pageup and pagedown on your keyboard to find your quest that is stuck, in my case Favor154. Type Player.sqs Favor154 in the console to see your progress (stage). Finally, type SetStage Favor154 20. 20 is the stage that was stuck for me, the dialogue with Siddgeir.