As an irregular verb, the word hamstring can be used either way.
TO hamstring, Have hamstrung.
My English teacher once told me that when in doubt, sound it out. To me, “hamstringed” clangs.
I wouldn’t pay that English teacher no never mind. Lots of things “sound right” to lots of people.
The “string” in “hamstring” is not derived from the verb “to string.” It is the name of a part of the body. Thus, the verb “to hamstring” is analogous to “to gut” or “to skin.”
A person who hamstrings is not doing any stringing of anything—he is cutting. I.e., cutting a hamstring.