So, there is an agent that is putting property in the MLS and then changing the status from "Active" to "Hold" but when called is saying that the property is "In Escrow" - how should that be dealt with?

call the association with as many details as possible ... also on the mls at the bottom of the listing there is link " if you believe there is a violation...." .. click on it and submit so the mls can be aware also and reasearch ... change will only happen if things are reported

I would contact You local association. I had that happen once, they are trying to double end it. NOT doing their fiduciary duty to the seller.