Frequent hamstring pulls

I cannot consistently workout hamstrings without pulling them. I've had periods for a few months here/there with success but it's only a matter of time. RDLs, stiff leg deadlifts, hamstring curls....even lighter weight, selectively doing one of these, eventually they will bite.

Probably somewhat of a flexibility issue but I cannot consistently stretch out my hamstrings more than to a mild degree without pulling them either. Apparently I have weak, ginger hammies but I'm not giving up on them yet. Anyone here overcome gimpy hamstrings?