Having had similar symptoms on my +4 with the same remote it is well worth replacing the rubber bushes (even if its the grub screw) when you have the gearbox cover off. I replaced mine with polyurethane, very cheap and easy once you have taken the interior out.
The gearbox cover is usually trapped in by the prop shaft cover, not a difficult job, just intrusive.
LT77 or R380 both have a similar remote with the same bushes.
