Temperature ?
Species ?

See sbryce's wandering Perionyx excavatus . . .on a forum near you waste of words . . . on this forum

Yes harvesting encourages worms to wonder. Many vermicomposters discourage this by leaving the cover off so the sides will not be so damp and leaving on a room light. Many vermicomposters end up not using covers unless they stack bins.

Whenever I change things around in the bin I always leave the room light on for a night or sometimes three. This is to prevent the worm ladder I did see once where the worms made a 1/4 inch wide ladder of their body mass straight up about 18 inches of plastic to the top of the bin. I do not know why they all organized themselves so well. Maybe decomposition gasses encouraged them onto the high ground along an edge and they kept on going.

Your new additions might be to hot for them?

You dont say how many worms you have, possible they are looking to expand the herd. Yes its true especially plastic tends to sweat more if a cover is left on tightly. I find If I leave my lid cracked slightly it does not sweat on the inside at all. Currently my plastic bin is triple stacked.