Plated Mounting Hole covered by SolderMask

Update: Moving the Incorrect Hole(Hole2) in towards PCB center by 0.5mm seems to resolve the issue. In the earlier(Incorrect) situation, Copper pad of hole was touching the PCB Outline while there is a gap of 0.5mm between PCB Outline and PCB Copper plane.

And after moving the Hole in by 0.5mm, Copper pad of hole is within the Copper plane circumference and thus, looks OK.

But the strange thing is the Correct Hole is also lying in the same position i.e. its pad is touching the PCB outline and there is no issue there.

This must be something to do with the pad definition (check to make sure that the pad isn't using a different padstack name). I have a design here and if I move the pad edge to touch the board outline it displays correctly

If I move the hole so that the actual hole is beyond the outline it breaks the outline

So check the soldermask layer as well as the soldermask definition for the padstack. 

Hi checked the padstack and it looks like this on all holes:

Drill diameter of this hole  is 3.2mm and plated. PCB is 8 layer.

OK maybe you could upload a simple version of the board with just mounting holes and outline so we can take a closer look

I see that the incorrect hole(on left below picture) is not showing Soldermask opening over/around the pad/hole in 3d canvas while the other 2 holes do. I checked the Pin>Solermask Top in Board File and there are Soldermask over all 3 holes.

ok. can you send me your email address so that i can share it. 

I see that the incorrect hole(on left below picture) is not showing Soldermask opening over/around the pad/hole in 3d canvas while the other 2 holes do. I checked the Pin>Solermask Top in Board File and there are Soldermask over all 3 holes.

ok. can you send me your email address so that i can share it. 

Not prepared to put an email on a public site so you can upload your board onto the forum. If you don't want to put it here make a simple example (just the board profile and mounting holes) and upload that.

OK

You have uploaded a step model, I need to see a board file so I can look at this in Allegro.... 

OK. I made a gerber file out of board. Believe this shows all the info you need.

5857.SM_Pin_TopBottom_Outline.zip

A Gerber file won't show the the padstack etc. Make a new board file, copy the profile and fixing holes ONLY into this board file (view it in 3d and make sure you see the same issue) then save it and upload that so we can look at the board file.