Why can’t I split anymore parts of my video?

I'm not sure why, but for some reason, I can't split anymore parts of my video. I have a bunch of split parts of my video right now because there is a lot of editing that needs to be done. However, I tried to split a part of my video after all of the other splits, and I received an error message (yellow triangles with exclamation points in them on all of the thumbnails for my video frames). I don't know if this is because you can only split a video so many times or because my software doesn't work or what. But every time I try to split that part or any part after it, I see the error triangles. And once I undo the split the error goes away. Please help!