Christ!! First look at the amount of history build up in the channel box get rid of that lot first then attempt to re split the edges. Failing this, make sure all geometry has merged verts. If you are trying to split this using MJpoly tools it wont have it as theres a five sided+ poly in the hole and around it, it really need edges putting around the other holes too, looks like 8 to 10 sided polys!! Not very good


Also what has been suggested by Nitroliq is the easiest way to avoid any probs. You keep the shape and the geometry tidy every time if you think about it.

Jay