I recently got a 2018 Felt VR30. I've been riding for a long time, but this is the first bike I've ever had with a carbon fork, and only the second I've had with a threadless headset.
The problem I'm having is that the stem keeps creeping up the steerer tube; this pulls the plug up as well. Every few days I need to tighten everything up, and tonight I noticed that the headset's upper cartridge bearing is loose in its race.
I am concerned about over-torquing the clamp bolts, but I'm doing it anyhow, because 5 nm just doesn't seem very tight. I've applied some carbon paste to the steerer, which seems to help a little, but it hasn't solved the problem. The stem (from Ritchey--not stock) has visible loctite on its bolts, but maybe they need more? It occurred to me that it might have a different stack height than the stock stem, and I've played around with headset spacers, but that doesn't seem to make a difference.