Unresolved normal gap after FBX exporting

[diolee]

Hi,

Our project has developed with FBX 2012.2 over 3 years. everything is perfect until this ugly normal gap appears. I mean this is not the regular normal gap.

Here is what happens after exporting(middle of neck):

Here is what looks like in 3dsMax2010(64bit):

 The head and the body use two normal maps and have two different UV on their own:

 

Any other type of gaps I already handled with and resolved(like UV edge). In this case, In 3DSMax it's all right by after exporting of fbx it's not right. BTW, I didn't do any vertex merging after FBX exporting.

So I guess perhaps, just perhaps the reason of this issue is the FBX version is too old, you guys have been solved this issue already. or this is a FBX bug, you could handle with it some day.

Please tell me how to deal with it, please!

Cheer.