I ride with Clubs most weekdays and weekends and am comfortable and experienced with riding in groups. Now I might have a answer for your problem. One reason why I ride in groups is ok I like the companionship but I also love to paceline. Since you said you always ride somewhat off the last rider, it's possible you are breaking down the paceline. I have been known to ride around someone who won't maintain a paceline to make sure I stay with the "train." Once off the back you are lost forever.

Just something to think about when riding in groups. I know lots of newbie and less experience riders are very cautious and don't feel comfortable on the wheel of the rider in front. I personally will not paceline off someone I don't know or know doesn't ride safe but if behind one of my buds who I ride with regularly, then I am on that wheel and hanging on for all its worth. Also if someone rides alittle "squirrelly" doesn't maintain their line, I will either pass or drop back.

Don't take it personally. Next time it happens see if the group was not pacelining. If so, then you either need to hone your skills or drop back and allow those that want to hang on go for it. Find some riders that also don't like to paceline and hang with them. Group mentally sometimes takes over - people don't want to be dropped and will do anything to stay with the pack.