If an inhabitant of a tangent invents a tangent-travel device and it quietly starts spreading, such disruptions might become progressively more common in neighbouring tangents.
Did anyone get the sense that certain unheard-of events had suddenly begun occurring repeatedly, with no apparent connection? I could mention several examples, perhaps least controversially, dressing up as scary clowns
. We blame Facebook, but maybe it's actually multi-parallel outside interference. The perpetrators might be quite happy to put themselves into grave danger, knowing that the cause will carry on reliably under other versions of themselves