Cannot move rows except certain rows up or down while customizing form

On the customize form screen, while customizing Sales Invoice Item, I can only move 3 rows namely Is Non GST, HSN/SAC and Is Nil Rates, rest of the rows are not moving. What is there I am doing wrong or incorrectly?

Update: Only rows at 5th, 6th and 7th position are moving irrespective of name, rest are not.