What armors come with the Falskaar mod

If you're playing on PC, you can try to install a follower overhaul, such as Ultimate Follower Overhaul (UFO) or Amazing Follower Tweaks (AFT). These should allow you to remove your follower's equipment.

It sounds to me though that your save is glitching out, something that often happens to very old, very long saves. In that case, and IF using the follower mods doesn't work (please don't try them at the same time) then you can use the save cleaner to try and clean up the game scripts on your save.

As with everything, make sure to back up your game before messing around, especially when it's in a delicate state.

So it actually seems to be not "unique", since it was encountered at least once in the exact same configuration by someone here. As in my case, there was the same combination of mammoth + dragon attack.

The elder scrolls wikia also mentions the bug of Skjor coming back, dead and clipping through objects.

Companions were also seen wandering far from their place here and here.

So my guess is: it might be implemented in the game that Companions go at random places in Skyrim to hunt big hunts (after all, they are supposed to be the mightiest warriors). Maybe it is triggered by becoming a Harbinger, maybe not (would need other conclusive proof).

Skjör seems to come back often, it might have happened in my game without me realizing. It seems to happen to Kodlak too from time to time. Being close, Njada followed and helped them too.

Both her and Skjör joining might be an effect of the CompanionFactionMinusBrillAndVignar faction. This faction thing could actually be the reason behind Skjör and Kodlak "resurrecting"

Edit: video of the bug happening: here and one with a variant here