Duplicating vertices when using CREATE on the first call

[ilyaaid]

Hello!
I'm trying to create a vertex named Pam now.
Command CREATE (pam:Person {name: "Pam"}); creates duplicate vertices with name "Pam" on the first call.
Moreover, on the second call, the same command creates only one vertex (this is the expected behavior). As a result, instead of two vertices, three vertices named "Pam" are created.
Everything works normally in the Neo4j browser.
Could you please explain what can be the reason for such behavior?