[Private]

When I made the ticket, I thought that the redstone wasn't being activated in one specific chuck. Had I known it was actually anywhere within two chucks of the border, I would have probably have found that other ticket in my searches. Thank you very much for your assistance, though.

'Ello.
Have you tried upgrading their rank? Once they're playing, have the world host change their status from "visitor" to, say "operator". This should fix the issue.
Note: their rank may actually be "custom". If so, try customizing their custom rank.