heli's don't despawn and more than one cargo ship spawns?

The only standard entity with a hard limit in the game engine is the bradley.  All other entities do not have a limiter built in,  I have run events with 5 cargo ships active on my server and it test have had 20 (not recommended due to the lag).  We do not add any limiters and leave that to the operator to decide what they want to do.

We do not run a despawner, these are vanilla entities we spawn in, so they use their normal in game timer for their expected life time.  I personally run bradleycontrol and helicontrol to tune them beyond vanilla.  They also some times glitch out (are invulnerable or do not despawn).  So I think it might be a rust game engine bug, not a bug in the coding.