In fact when xCon iOS 10.3.3 is installed it broque Cydia on iPhone 64 bit Jailbreak whit h3lix.
And you see "preparing filesystem (cydia will exit when complete) and nothing happen at all ; it crash and it's over for you.
If by mistake U did it wowww U are in trouble , Cydia doesn't start anymore , terminal is also Lock and unusable , if you got Filezila u can remove the package easely , if no , well it stay Cyberduck then go to :
I fixed this by removing xCon (deleted i mean) to do this: Remove, erase from
Reboot and Cydia works like a charm and U saved your jailbreak
If it can help someone , I'am on macpro so I use Cyberduck but it will be the same thing to do on Windows 7/8/10