You can check more information, including the last modification date through the "regular" github link
https://github.com/openwebwork/webwork-open-problem-library/tree/master/OpenProblemLibrary/Rochester/setAlgebra35SystemMatrices
The particular problem solve_3x3.pg was fixed 2 months ago, but you would have to check if the bug was the one you found, or another one.
Some of the bugs are fixed the same day, some others take three months.