So I went out and spent 10 minutes detecting yesterday evening with the Gold Racer. Didn't notice anything out of the ordinary other than the ground sounded much different wet compared to dry. Dug a few bullets - was just wasting some time.
Before I put the detector away, I wiggled the connection to see what it did - it acted similar to the video (perhaps a little worse since it generated a target ID #). My connector nut was not tightened. Who knows how long I had been using it that way!
After tightening the connection, the behavior went away completely. I suppose if I molested the connection a bit, it may still have affected the threshold tone, but I have a policy of not wiggling connections unless something is broke.
I want to say that my Fisher Gold Bug 2 does something similar, where you can hear a change in threshold when you wiggle the connection.
I avoid doing that and keep on finding treasure. Truthfully, with the cable properly secured, and under normal use, I highly doubt your connection behavior would affect performance at all.
However if it were me and it WAS affecting performance I would do the following:
1.) Turn the detector off and remove batteries.
2.) Look at the threads of both ends of the connection. See if there is anything that is preventing the connection from threading on further.
3.) Lightly apply a little dioelectric grease onto the male threads and tighten and loosen the connection repeatably, working the threads. Don't over tighten!
4.) Remove the coil connection and with the connection pointed downward, heavily spray electrical cleaner into both sides of the connection to wash out any dust or residue that may be in there from normal use or manufacturing processes. Also wash off the grease from the threads.
5.) Immediately gently blow compressed air into the connections to evaporate the cleaner.
6.) Carefully secure your cable to the shaft at several locations, including the base by the coil and near the connection.
7.) Re-install batteries and check for improvement.
Personally I think that connection style could be updated and improved.