I have this problem where turned off surfaces, that are not visible in the model, get in the way of my work. They are selectable and I can hide it but after awhile they appear again; as invisible but when I try to do something that is behind them they are preventing me from selecting. There used to be one only in the model and although annoying it was so bad. Now I have a lot of those invisible surfaces and it is becoming very painful to work. Does anyone know why this is happening and if there is anything I can do to have the hidden surfaces be hidden for real?