Why can't my multi-instance use variables

I have some multi-instance tasks where people are specified through one of the previous task forms.
And I converted List to JsonNode type and saved it.All values in this collection are user ids.
But now there is a problem,I found that the process engine parsed the elements in this collection in double quotes, making it impossible to assign tasks to users.
For example,List is just like [“user1”,“user2”],but the engine will recognize it as ["“user1"”,"“user2"”].
Has anyone had a similar problem?How can I solve this problem?

Can you share the bpmn xml? How are you passing the collection and what type it is? It looks like it is an ArrayNode?