I'm not sure if this is a common problem but it might be worth giving your bike a check.
I noticed the front brake was binding a bit so I decided to take it apart. I expected to find a stuck piston but it turned out to be this pin which holds the caliper.
The caliper holder pin had to be forced out of the caliper. this shot shows some corrosion that had built up.
The rubber boot had been squeezed onto the pin. You can see that the boot has been deformed with some corrosion embedded in it.
After cleaning off the crud I had to buy a new set of brake pads (over £40) as one them was worn right down. Worked in some ACF50 around both rubber boots afterwards.