What twine are you using. Many the old balers do not like the new neoprene twine and will only work with the sisal. is one roll of twine old? If you know how a knotter on a John Deere baler works the New Hollands are pretty similar. Where is the twine breaking? The end being held by the knotter or the end being delivered by the needle. Sounds to me like the knotter is not holding the twine tight enough. A little adjustment might fix it.