Subdivision Surface modifier skips some parts of mesh

So I am exploring ways that I could use subdivision surface modifier. In these two examples I have noticed that subsurf modifier is not behaving consistently. Possibly someone might know why.
Example on

One arm of this does not want to subdivide:
treeshape.blend (820.4 KB)
And then on this shape from a ico sphere equally expanded out

Here above one of these legs is being ignored by sub-d modifier all the rest are rounded out but not this one. (upload://vMdM3LGwEL9OCWtAc9KZ6vhdF4h.blend) (784.6 KB)
So weather I make a tree or a set of antlers or an octopus it looks like sub-d is not going to work out to model these types of items. ?? but maybe I am doing something wrong. ?

I wonder if this might be due to my gt520 video card or my hardware - I am on my tv system and its only a opiplex with a i5 and cheap video card. Maybe my hardware has something to do with blenders behavior ? later today I will try these again on a 1070 ti

You have duplicate vertices in that area of the model. Select All. M>By Distance

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Sweet Thank You ! That fixed the issue thank you John

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