Slices won't show in certain times

[Cal1270]

If I put over a certain number of transducers (approximately 25X25), slices won't show! I've tried many times and I really don't understand. Is there a way around this?

I can still calculate traps on the slice (that I don't actually see) and see the phases of the transducers / the value of amplitude.

But overall, this software is amazing!