SureAI

During the quest "The Chains of the Deep", there is a sequence where you shoot a mechanism with a bow and arrow to obtain a speed buff, to allow you to run over the lowered drawbridges fast enough to reach the portal before they rise again. However, for me, this buff did not go away when the spell duration was over. I permanently have an invisible +100 buff to my speed, bringing my total speed to 161. This buff does not show up in my list of active magical effects. That list is showing me as only have a speed buff of +1, from my Destruction Greaves. Thinking back, I may have activated the portal before the spell had ended, and I suppose somehow that could have locked the buff onto me. Not that I'm complaining too hard, it is nice to be able to run faster than horses even with my weapon drawn, but it is getting to the point where traveling with a companion is a game of sprint-and-wait. Is there a way to remove this buff using the console? Has anyone else experienced this bug?

No, this should not have done so! I have activated the portal before the spell has ended several times, and hadn't this bug any of them.

You are not the first to report the bug, but nobody has yet been able to explain how it occurred. Maybe it's some engine bug occuring randomly...
But before we are sure, maybe you could help us by telling us:
- Have you autosaved or reloaded while you had the buff?
- Have you loaded a save in which you were just having the buff?
- Did you level up while you had the buff?
- Did you have some disease while you had the buff?
- Did you apply some spells acting on your attributes and skills while you had the buff?
- Did you cast Dispel while you had the buff?
Thanks a lot for any help!

To get it removed from your savegame, I think the following two commands should suffice:
player.modav speed -100
player.modav athletics -100
(The latter only if your athletics is similarly perma-buffed.) I HOPE these work.

To make things simple, when I say "i had the buff", what I am referring to is the time that I was SUPPOSED to have the buff, when the icon for it was displayed in the top-right of my screen, and it was listed under my active magical effects list.
When I had the buff, the game did autosave. To my knowledge I did not use any spells while I had the buff, nor did I exit the game, reload a previous save, or have any disease. I DEFINITELY did not level up during the time I had the buff.
I feel like I may have shot the buff trigger mechanism twice, perhaps shooting it once, pausing the game, then returning a few minutes later and shooting it again, not remembering shooting it before I had paused the game.
The console command you provided worked perfectly, so thank you very much! I hope the info I gave will help you isolate the source of this bug!

Because you know: everything worth shooting is worth shooting twice

Thanks for mentioning that - that *might* be the problem, although I wouldn't expect it to be. I'll look into it.