Experiencing a bizarre, extremely specific weapon damage glitch.

[Ches]

I noticed that the attack power of what seems to be all of my archery weapons (and only archery weapons) dipped by ten points in one of my recent saves.  I had no idea what caused it, but I went through the effort of testing to see if it was a disease or other status effect, or perhaps the result of some article of armor or clothing I may have accidentally equipped or unequipped (it doesn't seem to be).  A few hours of experimenting later, and I've traced my playthrough back to the exact moment at which my archery damage drops.  Yet I still have no idea why it happens.

 

At exactly 5:37AM on a certain day, the damage on my Dragonbone Bow, for example, instantaneously goes from this:

 

 

 

to this:

 

 

 

I've reproduced the effect a number of times by now just to be sure.  And I have absolutely why it could possibly be happening.  I'm not even sure if it's actually related to the game's internal clock or if that's mere coincidence, but it's always at 5:37AM that day.

 

This is vanilla Skyrim, plus Hearthfire and Dawnguard, by the way.  Not a single mod installed for this playthrough, as it's my main.  And I also verified the game files to see if it might help, which it didn't.

 

The damage difference is minor enough that it's almost negligible, but it's extremely irritating, and I'm worried that if I don't understand why it seems to have randomly dipped, it might happen again in the future.  If this were to happen a few more times my archery skill would be totally nullified.

 

What on earth might be happening here, and how might I be able to correct it?

[Fotogen]

On your screenshot you went from Damage: 93 (+77) to Damage: 93 (+67). Number 77 and 67 are green. That a usualy 'buff'.

 

Maybe one of you buffs expired. Buffs have duration. It would explain why it happens at a precise day/hour.

 

You can see the list of active magic effects for your char in one of ingame screens. Or not. Thing is, in CK (Construction Kit) I can make a buff (magic effects) and flag it as 'Hide in UI'. This would make it 'invisible'.