In my previous playthrough, I noticed that Lydia was able to carry less and less for me as my game progressed--- eventually reaching the point where she couldn't carry anything at all.

This time around, I noticed the same issue with Argis the Bulwark. So, I began testing and I noticed that every time I dismissed and re-recruited Argis, his max carrying capacity would drop either 6 or 8 pounds (it seemed to alternate between 3 and 4 pounds with each dismissal/recruitment).

I tested this with leathers. When I started testing on Argis, I already had him equipped with Ebony armor, helmet, gauntlets, boots, and a greataxe so he was already carrying a fair bit. On top of this he was able to carry 31 leathers (weighing 2 pounds each). I dismissed him and recruited him again, at which point he could only carry 27 leathers. Then 24, then 20, then 17...etc. It alternated between 3 and 4 leathers (6 and 8 pounds) every time I dismissed/recruited him.

Anyway, I was hoping someone else could confirm this through some similar testing of their own. I'm not sure if this glitch is specific to just Lydia and Argis, or if it's all the Housecarls, or if it affects every follower in the game.

There's a bug that causes the game to spawn a whole new set of default armor on your follower every time you hire them again.

You can use "showinventory" command to check this.

And "removeallitems", "disable" and "enable" commands to remedy this.

If you are playing on consoles then only solution is to wait for an official patch.

Ah, that's what's happening, Thanks!