Sony Sound Forge 8.0 recorder

:bow:Hope someone can help me… I’ve started to take records from radio via Sound Forge 8.0. The line in input is a very clear signal but while I’m recording, after about 4 min, a low level cracking noise comes up and is very annoying. I could not identify what it is but on Sony Acid pro recorder it does not happen. It must have something to do with the program - a setup I believe. I like the Sound Forge recorder and still want to use it but not an alternative!