I'm not sure if this is really a bug, or just how the system works..
At what points does your encumbrance get recalculated when doing things that affect it? Picking stuff up, casting spells, etc?
One thing I have seen several times is casting BES by itself doesn't seem to affect my burden, but once I type enc after casting BES my burden does change.

Not sure if there is a flag that can be applied to a spell that will cause it to recalculate encumbrance, or if all strength/burden spells behave the same way and there isn't an easy way to have it recalculate.

Here's the scenario where I discovered this..
I load up on crafting supplies and head up to the trail going from near Rossmans/gryphons to just north of Lang.
Scout trail, go trail..I get a message indicating I can't go..offhand, I don't remember if it says anything specific to burden or that I'm just in no condition to go. My burden is so big that I can barely walk so I know it is the reason.
I cast ease at maximum mana, scout trail, go trail..still too burdened. I check my encumbrance. Yep, still way too burdened.
I cast BES at maximum mana, scout trail, go trail..still too burdened. I check my encumbrance and see I shouldn't be too burdened, try scout trail, go trail.. it works. After typing enc, I am able to go.

I haven't tried it in reverse order, casting BES first to see if ease burden also behaves the same way.. not sure I could maintain a 30-mana BES while prepping to cast ease at max mana.

The specific scenario above is something I did once every couple of days over several months, so I'm fairly sure it wasn't just a fluke or a timing issue. I'm used to it now so it isn't even a complaint.
I guess I am mainly wondering when the encumbrance change takes effect.. I always think they take affect right when I cast them, but as far as I know I could still be traveling/hunting/whatever with a larger burden just because I don't type enc.