Hi there!
I setup an automation rule which is triggered by "Sprint created" and creates both an Xray "Test Plan" and "Test Execution issue". Also both issues should go to the sprint which triggered the rule. Here the "Create issue" step of that rule:

Rule is triggered successfully and both issues get created but they are NOT assigned to the triggering sprint. Audit log says:
Action details:
Unknown fields set during create, they may be unavailable for the project/type. Check your custom field configuration. Fields ignored -
Sprint (customfield_10020)
Issues created successfully
ABC-123
Our Jira admin could not find any setting to check or change. Pls. give some hints how to solve that issue.
Thx a lot!
Martin