Shimano Stradic FH - bail closes on cast

I have this Shimano Stradic 2500 FH that for some reason 3 out of 10 casts, the bail closes during the cast. It was professionally cleaned this year and still continues to do it. I own 3 other shimano spinning reels and none of them do this. Anyone have this problem and how did you get it repaired? I prefer to keep it. i would like to sell it but don't want to pass on a problem. But if I can get it fixed, I'll keep it.