Multiple users claim the same ticket

I got complaint from users that they were able to claim the tickets and replying to same user. How could that happen?

my system is 1.15.2 running on CentOS Stream.

Users cannot claim tickets, only Agents can.

Quite literally Agent A claimed the ticket, then Agent B claimed the ticket.
There isn't anything that prevents this action from happening.

thanks ntozier. I meant Agent, not user. I tested two scenarios,

both agents open the unassigned tickets at the same time, and claim at the same time. One of the agent was not able to claim it and screen freeze. And after refreshing, it found that other agent was able to claim it.
both agents are on the open tickets list screen. They both click on the check box of the ticket and click on claim and they both able to claim it without any error.

thank you for your reply.