So called “cold spots” and falling objects are traditionally associated with paranormal activity, and usually with either human ghosts or stressed psychic people in the house, but not with Goetic entities, who tend not to hang around even when not dismissed. It’s possible your activity attracted a lesser entity in the area that’s now camping out there and enjoying a free lunch 
Have you tried cleansing and banishing the area, and setting up wards to prevent unwanted individuals entering the space without permission?
There’s some info on wards in one of out long-term fave tutorials here:
I would give this a try, at least as a first step in finding out the issue. If it works it’s clear is was a ghost or other astral wildlife mooching off the energy of and around the altar. Kinda like ants at a picnic, there doesn’t have to be any malicious intent, they just want some of what you’ve got going on. 
So you can just shoo them off.