I'm having some weird issues with landscape.

Here what i have done:

I have created a 1009 x 1009 landscape and after sculpting it, i can see seams along the edges of all components.(I have added the material as well but still seams)





One more thing, when i change values in DRAW SCALE, the collision on landscape doesn't work and player just falls through the landscape and also the landscape brushes gets buggy while sculpting.

Any Clue on this?