I have noticed an extremely annoying and game breaking bug involving the summon arvak and durnehviir spells.

If you cast one of those spell then enter in interior cell with a loading screen while the spells are still active the summons are not only still there when you leave the cell but are permanent.

I have a permanent arvak outside Lakeview manor but more annoyingly I have a permanent durneviir flying overhead which is annoying the hell out of me.

Is there anyway to get rid of these permanent summons. Particularly durnoviir?
If there is no way to get rid of him I will have to go to an earlier save and do the whole diplomatic immunity quest all over again because I summoned him before starting itand entering the embassy.

Have you tried killing them?

I've tried shooting him with arrows but the seem to be having no effect

If you summon him again, does it summon a second Durnehviir? If not, there's your solution. If so, a ) awesome! and b ) maybe they'll kill each other b2 ) that would be awesome!

I'm just going to have to reload an earlier save and lose an hour of gameplay.

This bug is extremely annoying and game breaking. I'm wondering if other summons are effected by this bug?
Although other summons can probably by killed but a permanent durnoviir is just plain annoying.

Already tried that. When you summon him again the new durnaviir replaces the permanent one. When the new one times out the permanent one comes back. There is no getting rid of him

Strange. I'll see if I can recreate that.

I couldn't specifically recreate your situation because I don't have any characters on Diplomatic Immunity that can summon Arvak or Durnehviir. However, I did test summoning them and going through loading screens.

I summoned Arvak, then Durnehviir, overwriting Arvak and Arvak exploded in death.

I summoned Arvak and walked into Snapleg cave, immediately walked out, and upon Arvak's timer's expiry, Arvak expired.

I summoned Arvak, walked into Snapleg cave, waited until his timer expired, and walked out. Arvak stood there for a second, then collapsed and expired.

So, no trouble with Arvak and caves that I could recreate. I tried those same steps at the gates of Whiterun, and Arvak never followed me into the city, and had no permanent Arvaks to speak of. On to Durnehviir.

Durnehviir seems to expire after 3 hours of game time. So, at Snapleg Cave:

I summoned Durnehviir, walked into the cave, walked out, and waited 3 hours. Durnehviir expired as normal.

I summoned Durnehviir, walked into the cave, waited 3 hours, walked out, Durnehviir was waiting for me. I waited an hour, and Durnehviir expired as normal.

No trouble with Durnehviir and caves, so I went to Whiterun.

At Whiterun, I summoned Durnehviir, and walked into the city. Durnehviir followed me, and flew around the city for a while. That was interesting, so I let it play out. After 3 hours of game time, Durnehviir expired as normal.

I even managed to glitch myself into summoning Durnehviir while in the city (which you normally can't do) by engaging conversation with someone immediately when the second word of the shout is spoken (provided the space behind the person with whom you're engaging conversation is adequate for the summon).

So I tried some other things. I summoned Durnehviir inside, went outside, waited 3 hours, Durnehviir expired.

I summoned Durnehviir outside, went inside (Durnehviir followed), waited an hour, went back outside (again Durnehviir followed), waited 2 hours, Durnehviir expired.

So far, I've been entirely unable to create a permanent Durnehviir or Arvak.

Weird i've been able to create perma arvak and duneviirs every time.

Do you have Hearthfire installed as well?

It was going into my house i built in the dawnstar hold when i first noticed I could create perma arvaks.

Could this be a bug added by hearthfire or could there just be a strange problem with my save?