When two people pull a minicopter in a row at the outpost, the first person who pulls a minicopter loses their minicopter. Does this plugin fix that too?

That is not a bug in vanilla Rust as the vendor will not allow purchasing a helicopter for several minutes while one is occupying the heli pad.

If you are using a custom map, then you are experiencing an issue where your vendor is not synced with the heli pad therefore does not know whether a helicopter is on it. That is fixed by https://umod.org/plugins/custom-map-vehicle-vendor-fix