For original research, a researcher is supposed to replicate studies that form the building blocks of their research. For example, if a drug is reported to increase expression of some mRNA in a cell, and your research derives from that, you will start by replicating that step, but it will just be a note in your introduction and not published as a finding on its own.

When a junior researcher, e.g. a grad student, fails to replicate a study, they assume it's technique. If they can't get it after many tries, they just move on, and try some other research approach. If they claim it's because the original study is flawed, people will just assume they don't have the skills to replicate it.

One of the problems is that science doesn't have great collaborative infrastructure. The only way to learn that nobody can reproduce a finding is to go to conferences and have informal chats with people about the paper. Or maybe if you're lucky there's an email list for people in your field where they routinely troubleshoot each other's technique. But most of the time there's just not enough time to waste chasing these things down.

I can't speak to whether people get blackballed. There's a lot of strong personalities in science, but mostly people are direct and efficient. You can ask pretty pointed questions in a session and get pretty direct answers. But accusing someone of fraud is a serious accusation and you probably don't want to get a reputation for being an accuser, FWIW.