Khrys did a deep dive into these meshes after 34523 and found a bunch of issues.
Long story short Khrys loaded the meshes and all the stuff they'd connect to in 3DSmax and edited them there to manually fix the edges not being the proper shape, which was the cause of the gap. In the process Khrys fixed a bunch of UV errors, vertex color issues, etc.
Note from Khrys regarding the edge fix "the fix approach applied handles these in such a way that if the model inadvertently buds up with other, different fit wall pieces, it should work in that situations favor"

Attached Files:
WRIntCastleWallStrTrans512_RevC.7z