Hello community,
I have always seen people go crazy for this problem which is solved with 2 lines of code, in particular with the various offlineshops (mine, or the free release great and ken) that are unfairly blamed for having duplication bugs. No!
I believe that if you warp a player on another core without performing any checks you can't blame those who made the other systems which are then used to take advantage of the vulnerability you caused.
If you implement something you need to make sure there are adequate checks to avoid causing vulnerabilities. In my opinion the cause of the duplication is not the various offlineshops, but the channel switcher which does not perform not even half checks before executing the warp.
Anyway, no more chatter.
I will explain here how to fix this problem.