Yes sure - you can download the dev kit from here : http://sebastianmihai.com/neogeo-neo-thunder.html

Look at the file "video.s" for the source code to the sprite functions

Also here is the official Neo Geo Hardware Specification manual : https://www.neogeodev.org/NG.pdf It has some examples for VRAM access timing in it (Page 10)

BTW have you tried reading the REG_VRAMMOD register to see if the modulo is set correctly still? Would be good to eliminate that as the cause