Are thimbles of large enough diameter?
Turnbuckles.
Any file cuts, tool marks, or flaws in shank or barrel?
Are there too many threads exposed?
Is turnbuckle of right strength and size to develop full strength of wire?
Are shanks bent?
Are threads on shank or in barrel well made?
Is barrel cracked?
Is turnbuckle properly wired?
Inspection of Linen.