Fulminato
Yeah, I imagine it is easy to miss that Iris' quest can be done early in chapter 5, given that it was only added in a later patch.
And I completely forgot Ardford could still be closed.
Another issue I found: Day 1 of the 2nd gathering, when bickering about the events the "support Esthera" option should give +2 Gathering Orgasmic instead of +1.
And a very minor one that will rarely be relevant: The Succubus Brothel Expansion Investment in chapter 4 (if you didn't get it via discretionary funding in chapter3) costs 50k ProN, but it will be marked as unaffordable whenever you drop below 500k ProN.
Edit: The Calculator thinks researching Tower Delving before the erosian war gives +2 HQ Magic immediately and another +2 when the research is finished. Researching it after the war only gives the +2 for finishing. I can't find any mention of the immediate +2 on the wiki. I guess that is another bug, unless you know of a bonus for researching this early.