Backpacks not working on first spawn for players

I'm having an issue where some of my players can't access their backpacks, and have to drop out of the game, and log back in for them to work... its not a major issue, but an annoyance.  if you have time to take a look that would be greatly appriciated.  
Thanks
James

Sorry for my delayed response. I could not reproduce this so far, are you still experiencing this issue?
Yes, and so are a few other server owners that i've talked to, but we can't replicate the issue on demand either.  It's literally a "random" issue that occurs... Sometimes just reloading the plugin will fix the problem, and other times the client has to drop off and rejoin the server... It's very weird.
Thanks for your replay tho,
James