Only thing that is 100% guaranteed to work is to get rid of the hogs

Usually it is one pig that starts the biting, if you can figure out which one it is and remove that one it will end. Finding the offender is a bit of a problem though.

If you ever find the solution to prevent/stop biting let me know what it is.

Seems like almost every group I've got at least 1 pen that causes problems and it's never the same pen either.