When a player leaves the mini on the cargo ship, it can get out of range of the player..

When the cargo ship despawns" where does the minin go?

If not destroyed, probably to the bottom of the ocean. I honestly suggest just setting the max nomini distance to -1 so you don't have to deal with the range feature.

maybe a reconfig of the plugin code to do that for the initial config file , for  users might be in order...
The only other fast way might be to test if it is wet