4th down and the rest of the field

is there a reason why occasionally you will have 4th down and say 2 yards to go, the little yellow line disappears you get 8 - 10 yards yet the ball gets turned over to the other team?
I have not found a pattern for this yet. And is something I wish they would fix. I think a support ticket would net some results as I am seeing more changes here recently.
okay Toptown.. next time it happens I will send them a ticket. thanks
you are welcome. Try to get a screen shot of the 4th down, it could help.