That's a vanilla problem: the bounty fleets generally spawn near a market-less planet. If that planet has a station though, there might be patrol fleets nearby that will take out the bounty immediately.
Assassinate bounties shouldn't end up like that, but they do.
And...well, when i said the bounty expire immediately, i mean the two messages pop out simultaneously like this.
somewhere:xxxxx credit bounty someone posted by someone on somebody.
bounty on somebody over.
Please forgive me for my unclear expression. It is my fault.
I just found that if this issue occurs, the portrait of the taget would must be a moded one. And I can't see Crystanitez in bounty fleets anymore so far.
Maybe there was a bug when a non-integrated faction trying to spawning some faction ships in the bounty fleet.