Camunda USER Task Complete

Hi friends,
I’m using Camunda 7.23 and encountered a strange issue that I can’t understand or resolve.

In our environment, there are scenarios where two users simultaneously complete the same user task via the REST API. When the BPMN model is structured as shown below, the user task completes, and Service Task 1 is sometimes executed twice, while Service Task 2 always executes only once.

In certain cases, Service Task 1 is triggered twice at nearly the same time (sometimes just milliseconds apart), according to the logs.

Could you please help investigate this and provide your insights? Thank you.