hi m8
heres a possible reason for your line parting..large swan mussles.i fished a 2.5 acre pond back home in east yorks and one season it didnt mater what i did in one corner of the pond i lost fish. sometimes the line parted without me even picking up the rod then other times i would be playing a fish then gone. the only way i found out was when i pulled in a mussle which had closed on my hook link.its posible this is your reason?????????????/