I don't know if this is a bug or not but it is very annoying...
When my character looks at a really bright light source and quickly looks away, everything is very dark and the screen takes about two seconds to come back to normal brightness. It could be just me but I doubt it since I remember someone else made the same comment on some website long ago.

I agree that its annoying but its most likely NOT a bug. That's how real life works. If your in the dark and someone shines a bright light in your face, it'll take a minute for you to readjust to the light around you. So it honestly feels more intentional, especially as a tactic the Dragons would use to keep you blind so they can eat you.
On Topic
Location: Valthume (Although could be anywhere. haven't tried in other places)
When Casting: Bound Battleaxe in Third Person
What: Mana is used up as though you cast the spell, but the Bound Battleaxe never appears to be equipped; and yet you look like you are holding it in your hands. Furthermore, you can't attack and even if you swap to First-Person you can't do anything except:
Interact with surroundings (Chests, pots, items laying about)
Shouts (Using R2 somehow still works)
Inventory and Start Menu's
Speaking of Shouts...
No matter what Shout it is, my character will only speak the first word in any three word shout. Although, the level 3 animation, time lapse, damage/effect is still applied. Just the Audio of the first word (and sometimes the second) is heard.
Level 16
Race: Kahjit Were-Wolf
If further information is required to troubleshoot, ask me and I'll answer as promptly as possible