HELP! Uv vertices welded!

[Jaumecampos]

Hi everyone! First of all this is my first post on the forum so I'm not sure if this thread goes here...

I've been using 3Ds Max for professional modeling since last months ago and I haven't got problems with uvs but two or three weeks ago maybe I started having some issues with uv unwrapping. It is a little bit strange issue and I've googled a lot but I didn't found any solution, in fact I didin't found anything similar to this. The case is that in theory in 3Ds max it is impossible to weld vertices on uvs that share the same edge or polygon but since some weeks ago Max is welding me vertices on the uvs that made me impossible to texture my objects on other softwares (specially on mudbox). Let me illustrate the problem.

In theory, the Uv unwrapping for that part of the model should be like this: 

But, when I made the unwrapping instead of having this, I have this: 

So I don't know if the problem is related with the properly uv unwrapping or with any other process of the modeling, or exporting, but that two verts were never welded on the model so I don't understand why they appear welded on the uvs. Note: I discovered that problem when smoothing the uvs on mudbox because if I apply a turbosmooth on the model the uvs are smoothed and the problem is automatically solved on the high res, but the lowres mesh still has the "welded vertices".

The only solution I've found for that is to break the concrete vertice and then weld the single verts again then making a simple relax by face the hidden vertice appears... But I can't find the cause of that!!!

I don't know why 3Ds max or uv unwrapping is making this on my models but since last two weeks that issue is occuring on every single model that I unwrap... I'm a little bit desperate and if anyone knows the cause of that problem I'll thank to let me know!

PD: Sorry for my english! I'm from Spain...

[ekahennequet]

Could you attach a scene file (must be zipped) showing just the problem area? You can delete other parts and just leave the offending area if this is a proprietary model.