if anything is going to fail using a bimini it should be your mainline, not the loop, the loop gives you twice the B/S of ya mainline, therefore ya mainline is the weakest between the bimini twist, loop, shock leader, rig body and snood, you must be doing something wrong somewhere mate for the loop to snap.
Just a thought here, when you say the loop, have you got it single, if so you defo got it wrong
you say the loop is just a loop of ya mainline, wrong, ya loop is then turned over to give you a double loop which is why you have double the B/S of ya mainline, hope this helps ya mate