If scientist makes claim that X sometimes happens... and then researcher Y repeats the experiment, and it happens a few times, but not always.... or not at the same frequency... far to many people say the replication has failed... instead of digging further.
There were many such incidents where the stated effect happened only a few % of the time.... but not zero. But, it wasn't 100%...so it got ignored, or rejected.
There were many such incidents where the stated effect happened only a few % of the time.... but not zero. But, it wasn't 100%...so it got ignored, or rejected.