Just curious, have you asked the researchers for their code? I've found that some people are willing to share their code and others aren't (some are just shy and embarrassed about how ugly it is, others have less justifiable reasons like it gives them a competitive advantage) Have you discussed your findings with them? Have you considered writing a comment outlining their errors (you might talk to your adviser about that)?

Refereeing is difficult to do well. On the one hand,in a Physical Review Letter, the article should be more broadly accessible, but on the other hand, it needs to be technically correct. I remember once reviewing a methods paper (different journal) and checking each equation and each integral (and finding a few minor errors) because it wasn't likely to be checked so much once it made it into a black box--but that took a lot of time! For myself, I've never had an editor tell me to "accept" a paper with errors. I have given a report and had the editor make a decision the other way, but that's different then asking someone to amend a report.

As for taking risk, I think the best advice I can offer is to have a portfolio of projects. I'm more senior in my career, but I did the same thing as a graduate student. Some things I work on have little chance of success, others more. This will vary by field and how expensive your needs are--but part of choosing an adviser (especially at the postdoc level) is choosing one that will allow you to explore your own ideas. I feel that my duty to postdocs is to offer some ideas that may work. If they have other ideas that they'd like to explore, then I view my job as to offer my expertise to support them...Micromanaging is too much work!!!!!!!!!!!