I have a stihl trimmer, edger and backpack blower, all 3 the fuel caps were jacked up on last year, to the point that it was a big frustration to attempt to get them off and back on. This gas cap debate has gone on around here for several years actually, and prior to the recall there was a number of guys that swore that the guys having trouble were severly brain damaged or something...
The reason some had more problems than others, it's where they live and how much ethanol is mixed in their fuel in that area! I got my new caps PRIOR to the recall, so they are the same caps, same O-ring, as the old ones. Since then I've been using gas from our Co-op that is ethanol free, whereas before I was just filling up the 2 cycle mix cans with regular or mid grade from the gas station down the street that has 6% to 10% ethanol. Since the switch of the fuel to ethanol free, and using the same caps that became a nightmare with the ethanol, I've had ZERO problems with these caps all year! Even through our EXTREME heat this summer the caps were never a problem to remove or replace.
The problem is just as Stihl has claimed, it's not really their caps, it's the fact that the ethanol content has increaced over the last several years, which they couldn't have known about this problem since it didn't exist before when the ethanol content was only a couple percent, or none at all. Ethanol is causing problems with all types of equipment and vehicles, a little o-ring swelling up on a gas cap is the least of the issues.