The way this worked was likely a misguided attempt at fixing #309 but without a real understanding of what was actually happening. Syncing bJetpacking to the client shouldn't be able to cause doubling of anything anymore (if it ever did).
Fix jetpack effect staying on when you switch class while jetpacking
- This will cause 'Server uses different class tables'
a nice trivial fix.. blast away... see what i did there half a year later