Is Porter stemmer working correctly?

I wrote a Python script to check the output of pattern's implementation of the Porter2 stemmer (in the vector module) against the output of the original implementation by Martin Porter.

Martin Porter provides a test input vocabulary of 29417 words and corresponding stemmed outputs of these words obtained from his implementation of the stemmer. My script compares the output of pattern's own Porter stemmer implementation with the output of the original implementation. A total of 215 errors were found. These errors are stored in the file errors.txt by my script available here. Sample preview:

Pattern implements the Porter stemmer in the vector module which can be used by first importing, from pattern.vector import stem, PORTER, and then running stem(input, stemmer=PORTER). My code is available here: https://github.com/ni9elf/PatternClipsExperiments

Start with the Porter stemmer implementation in pattern/vector and reproduce the comparison using the linked PatternClipsExperiments script and its errors.txt results. Compare the reported outputs with the original vocabulary and output files; done means determining whether the 215 differences reflect implementation bugs or expected behavior, with tests or a documented conclusion.