Hmm... very interesting. The biggest change I can see is, my order obviously has Update.bsa poorly listed and Fallout - Meshes.bsa is a lot lower than you suggest.
So after changing the order to match the above and resetting True Iron Sights I revisited every location I've currently been to with all the weapons in my inventory in my hand.
No issue with the arms moving all over the place.
I'm somewhat ashamed I had Update.bsa poorly placed but I'd never had to worry with it in pure FNV/FO3 games in MO. I will be more mindful of MO's quirks in future postings.
As for the capitalisation of the BSAs, that was my doing. After the creation of them I saw they were in lower caps and just assumed the fomod would copy them in and rename them. Since I didn't use the fomod, I just manually did it. Surely that shouldn't make too much difference? I made no change to the TTW BSAs. There was no "- main" appended to mine after creation.
So apparently it isn't True Iron Sights, it's MO's poor management of BSAs. Who'd've thunk it?
