Small Scubapro Twinjets keep falling off?

[moendave]

I'm curious if anyone else has had this problem. Both my girlfriend and I bought Twinjets for our classes (mine are large and yellow, hers are small and blue) and occasionally during our pool sessions she would have problems with her right fin working itself off of her foot. Multiple people have checked them for fit and said they fit well. Unfortunately, yesterday on our OW checkout dives her fin bade her a fond farewell and took off into the deep blue beyond :depressed: One of our friends is along for the trip and has been using the same fin for a year or so now and has had the same problem with a fin occasionally coming off... oddly enough always the right foot anyone else experiencing this? I'm wondering if the Twinjets just don't work well for little feet.
Thanks,
Dave