I am pretty sure this right, but I thought that would check.
When an ivesitigator moves back from one of the Other Worlds, the put an "investigated" token under them on the gate. If they cannot close/seal the gate, another investigator can move to that gate, and seal the gate.
Can an investigator "camp out" on an investigated gate (ie, not move out of it) - so it stays investigated - until another investigator can pick up a couple of clues and get there to seal the gate?
Mike