Just had some work done,normally I would dive in myself but I didn't have the time and the job would have taken me a week or more...
I was interested to note that all the compression fittings the plumber used have PTFE tape around the pipe extending from the fitting to a few mm out.
I remember using tape around leaky olives a few times usually because some enthusiastic "plumber" jumped up & down on his stillsons to get things "really" gas tight.
My only thoughts are that a layer of PTFE between olive and nut on a new fitting would lubricate the item a little and make it easier/ smoother to nip up.
I have had the odd fitting or two that isn't to easy to tighten and makes a noise akin to my knees in the morning when pressure is applied. Could this be the reason for the tape?