Like @COHIBA said and I will add on to "externally", refurbs are usually gone over with a fine tooth comb, most times it's just easier to replace everything internally than spend the man hours trying to track down the issues with "problem" units. The unit you get might be new B-stock.
Whatever you decide it is a pretty good response from Ableton most manufacturers wouldn't bother past the warranty.
I mentioned earlier my 10 year old Little Phatty doesn't have any signs of this. I thought I'll add I never set up it up by a window so sun never hits it, and I keep it covered always unless I'm playing it. So sun/UV seems likely… It's gotten pretty hot, was set up in a loft above a fireplace for 2 years.
Goo gone!! Seriously, it works. I had a set of jbl monitors that were horrendously gummy. After an hour with some goo gone, a roll of paper towels and a couple of beers I got it sorted out.
I tried the washable sticky lint rollers. It works.
It might come back over time. But for a couple of bucks/30 seconds rolling action, it's worth it.
Wow completely forgot about that!
Goo Gone is amazing I always keep a couple of bottles around.