One thing that was happening from time to time was the mouse accidentally registering a double-click when I had only clicked once. Presumably some contact bounce on the switch below the left button? I fixed it by setting the double-click speed on my laptop to the fastest setting. It does make it slightly harder to double-click but I have lost those phantom double-clicks.
The problem came back (and the awkwardness when
trying to double-click became annoying)!
I searched online and apparently it is a common problem with Logitech mice so I consulted online technical experts for advice (YouTube videos!) and found 2 proposed solutions...
One looked likely to work, but fiddly, and potentially fatal to the mouse - take the whole thing to bits, including the microswitch under the 'button' (in this case there isn't a button top, the top of the mouse casing is designed to just flex up and down for clicks), bend the springy electrical contacts, and reassemble everything.
Option two was much simpler. It seemed unlikely that it would work but several people in the comments section said that it had fixed
their mice, so I thought I would give it a go. That involved removing the battery and one screw to get the mouse open, and then applying a drop of lube to the little plastic rod that presses down into the microswitch to push the spring contacts together. The speculation was that friction was stopping the rods springing back quickly and smoothly enough to avoid contact bounce. I did this in the ad break of one TV show and to my surprise it seems to have worked. TBH, it was such a quick fix that if I had to relube it once a month it wouldn't bother me! I'm going to do a test... Before lubing the mouse, if I clicked once on each word in this paragraph, about one in eight clicks would have registered as double-clicks and highlighted the word. Hang on... Super - 0% accidental double-clicks, and 100% deliberate double-clicks, and that was with the double-click time extended to a more user-friendly length.