Been a couple years, but I don't recall any silicone on mine when I got it.
I don't remember any of my new machines having scuff covers sealed on.
I have had 4 or 5 gold machine I bought used where the previous owner sealed on the scuff covers. Some of those high kHz gold machine don't take to kindly getting any mineralized soil between the coil and scuff cover.
Sometimes when a machine doesn't act properly, checking for debris between coil and scuff cover is easily an overlooked thing. Some who don't check this on a regular basis might be surprised on how much can get in between there on some coils/suff covers. I've hunted with a few fellas who never thought of checking on this, or the coil wire connection tightness, or coil wire loosely wrapped where it easily moves above the coil, etc. (I like to use velcro wraps running the coil wire straight up the rod for a foot or so, then start wrapping the coil wire around the rod).
It's some of those little often overlooked items that should become routine. It's happened to myself is the reason I check more often nowadays. Or is it getting older I have more patience and take the time - bored - I dunno - but it's all good practice.