Vince
As Tim said , make sure that you have a full pull on the trigger , this is why i like a heaver trigger on my handi's , the momentum of the pull will carry on through to insure thet the t-bar stays up .
If your going to send it in anyhow you may want them to look it over , every once in awile they will have a weak hammer spring that will also cause this problem but this does not happen often .
One last thing to look at is the brand of primer that your using , some are harder than others .
stimpy