Rick, I feel your pain. Happened on the very first line I bought. One side of the spool popped off and coiled line went everywhere.

Since that day, whenever I need to spool a new line, the first thing I do is gently work it off the spool while holding the spool together with one hand. I lay the entire line out on the floor in an unoccupied room. Then and only then do I attach it to backing. Works for me.

Jim