`rank` is very slow for some matrices

I'm computing the rank of matrices with coefficients in a multivariate polynomial ring over `ZZ/2`. Most of the time this is quick, but sometimes it takes much longer. For instance, Macaulay2 1.18 needs about 4min to figure out that [this 32x32 matrix](https://github.com/Macaulay2/M2/files/6705409/rankbug.txt) over a polynomial ring in 5 variables has full rank. Sage can do it 150 times faster. Is this a bug?

No source file or test is named; begin by reproducing rank on the linked 32x32 matrix over a five-variable polynomial ring in Macaulay2 1.18 and compare the timing with Sage. Done should establish whether the slowdown is a bug and document or correct the behavior.

Written by the indexing model from the issue text.