Fortiswitch Port Update Problem

[rcpdkc]

Hello. Fortigate has versions 7.0.15 Fortiswitch 7.4.2. They are interconnected with Fortlink. My problem is the following. I plug machine A into any port of Fortiswitch. Then I unplug this machine and plug machine B into the port. When I check in Fortigate, both machine A and B appear on the port when only machine B should appear. What is the reason for this?