The indexes are all that matters, order-wise. Well, I mean the indexes must refer to the right vertexes, of course.
My advice, start with a much smaller grid to debug what’s happening and then increase it’s size a bit to see if your fixes still hold. I didn’t see anything obvious in your code above but I’m also not sure it’s really the same code you are still running.
Please paste the code where you assign vertices and indices to your mesh
Hi methusalah, the issue has been solved. I forgot to edit the topic. (I got banned, somehow 
)