Found another one… It's thieves' guild related.
Thieves Guild is apparently buggy as fuck.
The end of the main questline is really, really glitchy.
At the end, after you listen to certain someone´s speech, certain other someone -
- is supposed to talk with you, but that never triggered properly for me. Instead, that certain other someone spawned at the beginning and promptly left afterwards, leaving me in the chamber without means of interacting with anything and having to reload. Eventually I managed to get through it by some wait-for-an-hour antics, but after that the certain other someone never appeared in the location she was supposed to appear in.
During The Dainty Sload special quest, the contract giver wasn´t available at places he was supposed to be, instead he was leisurely strolling at the bottom of the sea
. Since I couldn´t interact with him there, I had to spawn him via console so that I could finish the quest and consequently close up the whole Thieves Guild chapter.
Actually, the game is rather buggy in general.
One other bug I experienced which rendered the major questline unfinishable was during the Companions´ questline where conflict with one of the side quests occurred - one of the quests in their chain took place in the fortress which was also a destination for a miscellaneous quest I´ve received previously (obtaining a helm for one of the jarls) and haven´t finished yet and that prevented the Companions´ quest to trigger. I had to check the wiki for that one and to repair the situation I had to storm the fortress and obtain the helm without killing the mini-boss there, return the helm and then use console to start the glitched Companions´ quest.
Speaking of Companions, there are few special quests available after the main chain is finished and one of these glitched for me as well - it was a quest in which I had to return to the same location where their main questline ended, but when I did so, the quest got automatically finished without me doing anything and rendered the object needed to
uninteractive in the process (thus if I wanted to use it afterwards I´d be SOL).
That one I fixed by reloading and taking a radiant quest from another guild member, afterwards it worked as it should.
There´s also quite a few glitches related to scripted events.
For example, in the beginning of the Mages Guild questline, during the initial tour, dragon appeared and broke the event in a way that the lesson which was supposed to take place afterwards didn´t happen, putting their whole main questline out of the picture (fixed by reloading till the event happened dragon-free).
A minor issue occurred right afterwards - once the lesson was finished and NPCs began to move to the other quest location I initiated dialogue with two of them and that broke their relocation. Luckily, it didn´t affect much, just the "now that you´re all here" speech was off, once dungeon was entered the two missing NPCs spawned there as they should.
On a different note, respawning has quite a few issues as well.
For example, ninroots in Blackreach respawned (but were unharvestable), a named NPC I killed as a part of one quest respawned after I´ve returned to the same dungeon to complete another quest, a note in the Labyrinthian´s exterior was also a victim of respawning mechanics and dragons respawned at certain locations (I think it´s only the locations marked with dragon heads) don´t yield a soul which may be a feature, but it doesn´t make much sense and when it happens it definitely seems like a bug.
I´d say respawning in general was handled in a very ham-fisted, lazy manner.
Aaaand I also got hit by the word wall bug (the "shout" theme plays, but no word gets highlighted). I could easily add the shout via console, but it still sucked because this occurred whicle I was hunting for shouts using Greybeards´ info and just adding the shout via console didn´t make the dude dispense other word walls´ locations, so I had to go the reload route since I wanted to keep receiving the hints (that specific wall remained bugged, though).
Also, while searching for a solution to the above mentioned Companions´ problem I bumped into a mention of a pretty major main quest bug - Season Unending has quite a few issues with Join the Stormcloaks/Imperials/Jagged Crown quests - if you plan to join one of these factions, better do the Join quest and the Jagged Crown one ASAP to avoid conflicts with the main questline.