Both of my Duros models had an enormous arm gap:

https://imgur.com/gallery/pG3XqI2

I don’t know if I somehow did this wrong or if that’s just how the models are. Anyway, despite my lack of sculpting ability I filled the gap with green stuff. I know I should re-prime the model but do I need to? Yes I’m lazy.

I had to use a little green stuff too on a couple of joints and no primer went anywhere near mine! Just painted straight over it and so far so good.

You should be fine on an area this small, just like with last minute mold line removal.

Any large gaps I found during pre-priming I tried to sand or cut the arm pegs. That takes care of some gaps. Failing that, I just used matte varnish to fill the small gaps.

I've found that problem on every Euros model so far but it appears to be that the arms mood is either widened or that they are widening after holding for some reason. I've found dipping the arms in warm water and resetting them works fine without the need for green stuff.

Mine too.

I filed down the arm joint "nubs" and go a way better fit, but still had to mix up some Green Stuff to fill in the gaps