Without even opening the FAR, I would think the
A&P would be at least partially at fault for not
making the repair in a "competent and workmanlike
manner", the minimal legal standard for *any*
repairman.

The wrench may not be at fault in any way, even a little. He/she could
have been competent and workmanlike all day, but if the parts provided
were of the wrong metallurgy, the problem will still be there. The
mechanic has to depend on the FAA doing its job to provide oversight on
the parts manufacturer and overhauler. If they provide the mechanic a
defective part/overhaul that has no apparent visible flaws (and all
required FAA pedigree paperwork), he/she has done their job. The
bushings may have been properly reamed and "free" operation ascertained.
But if the parts were incorrect, they would have galled up anyway.

Again, hard to tell with the available information.

Good Luck,
Mike