But tachyons are by definitions just “hypothetical particles moving faster than light”. Meaning if they exist, of course they move faster than light. I don’t know which lab your talking about, but people are absolutely right to think that tachyons are faster than light (if they believe tachyons to exist, which of course never has been proven).
Maybe you have the wrong word here and that people think that neutrinos can move faster than light, since there was a false measurement in CERN? But that one has been reported and updated already.