Their switches are just crap. They use Omron switches mostly due to their low cost, even on supposedly "high-end" mice. People routinely replace them with better alternatives (e.g. TTC Gold or Kailh, but there are lots of them) and get years of heavy usage after that without any problems. The switches can be obtained on aliexpress, you do need a soldering iron though.

It’s not just a soldering iron needed. I replaced the switches on my 17-year-old Logitech MX Revolution and on a newer Performance MX and the old switches are completely impossible to remove from the PCB without snipping away at them and a lot of (careful) force. However I can say that the result was worth it, no more phantom double-clicks. Mouse itself was fine.

Maybe for some of the newer mice it’s an easier ordeal, though.

I mean, if a mouse is working for 10+ years for 8 hours a day (M705) or for 14 years for 2-3 hours a day (G700) without any major problems, I wouldn't call that switches crap.

But that's only me, of course.

That sounds like a job for contact cleaner, assuming it’s possible to non-destructively get a tube next to the switches.

I’m about to open my second bottle. My first bottle is from the 1990’s.

No, it's a job for a sewing needle or a toothpick. Logitech switches can be temporarily fixed by disassembling the switch and adjusting the contact plate inside because it gets bent out of shape and stops registering the clicks correctly. But it's easier (and more reliable) to replace them with higher quality alternatives while you're in there.

The G700 in question registers clicks correctly for 14 years at this point. The problem in my case is very light clicks and dust ingress to said switches. I have 10+ year old M705 mice which doesn't have any switch problems.