Simultaneous events conflict

i'm making a plugin that gets entities and places markers on the map. it's triggered OnCupboardAuthorize(), so i'm thinking that 2 different players may authorise in a cupboard almost simultaneously, so there could be problems there with the code. is there any way to avoid this?
everytime the hook is triggered the markers are 'killed' and created again. So that small time difference between authorizations might be a problem.
Put it like this:

A - auths
B - markers killed
C - old data deleted
D - new data collected
E - markers created

player1: A -------------> B --------------> C -------------> D ---------------> E
player2: A-----------------------> B -----------------> C --------------------> D ----------> E

so we could get situations like this, where player1's new data is deleted by player2 triggered auth.
in this situation some player1 markers could've been created already, but it's data could've been lost halfway, and this happens when player2's event has already deleted the markers too, so we could end up with some markers which are not updated nor deleted from player1.