I've had the wave-style shifter grip for a few years now (five? can't recall the exact date), with no problems at all. Mind you, Matt, you've probably done a few more miles than I have.
In the realm of Other Fixes: I seem to recall George (mickeg) recommending applying about three strips of equally-spaced black Shoe-Goo from the inner edge of the grip to the outer.
(Note that black Shoe-Goo is not easily found--I have been unable to find a retailer here in Canada. Prices have also changed quite a bit in the last few years: today, a package of two tubes of the black stuff costs ~$50 + shipping from the U.S., and two tubes of clear shoe-Goo from Canadian supplier for C$22. No bargains there -- DIY supplies inflated by pandemic demand?
)