So I'm on my way to Sovngarde and just before I reach the portal I have to fight (or so I presumed) an Elder Dragon and a Frost Dragon, well they just repeatedly fly for three seconds then land (where I can't properly hit them) for one second. I hit one with my bow (that's all I have time for), it then takes off again and then by the time it has landed again it has healed itself, has anyone encountered this bug, if so, please help.

You can't kill them, or at least I've never been able to.

Purely aesthetic.

But there's no way through the portal :/

Well, fast travel back and forth.

Fixes some doors for me on occasion.

If not, I hope you have a save to rollback to.

Sorry, just realised what I had to do

Thats what the forums are for, outside of endless complaining...flaming... and trolling.

Grats!

You should have dragonrend at that point; use that to keep them from takign off. The dragon priest staff is the key btw