I don’t know what happen, While unwrapping my model (stairs), its Freezes the Texture Streching,it doesn’t effect on transition of UV points.

See Attachment for the File.

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maybe you have activated preserve uv on the move tool!

Maybe you switched to a different UV set without knowing it - make sure its set to 1

that’s a bug I think, does the render match the viewport?

That’s ok, there are 2 sets -
1. map1 - which is default, &
2. stairsnew - which is created by me.

ok when i changed it to map1 uv set , uv works, & when i change back to my created uv set, it freezes, why?

i opened uv’s, this is saved in map1 uv set, which is default.
now when i use copy uv’s to uv set > copy into New uv set option, it create a new uv set having the same uv pattern that i have opened in map1 set.
then as i select the new created uv set from UV set, the uv dosn’t works, as i changed back to map1(default), it works.

if i want to create a new uv having the base of map1 set, so , i can’t make a new uv set, therefore you have to work in map1 set only.
You can’t save different types of uv set.

You can use multiple UV sets.
You just need to use the UV relationship editor to connect textures to each UV set.
Maya Help has all of the info you need for using multiple UV’s.
That should be all you need to get this worked out now.
~Ben