split function problem driving me nuts

in X1d expanded. The problem: sometimes when i am working on a mix after an hour or so, the split function stops working or splits somewhere other than where I want it. and no, the snap function is not engaged at this point. I can't figure this out. please help !!!

That's the one..... extended mode.

That might be a different issue, the OPs is definitely because he is entering extended mode (by pressing 0 on the numeric pad)

It's easy to spot (once you know about it of course) because the split will happen just it splits in a seemingly random place. Try it you'll see what I mean. Press numeric 0 again to exit that mode and return to normal.