Jira expression conditions fail with “Action N is invalid” when the transition screen sets a field the condition checks

We have identified the root cause of the issue with the Workflow Functions service, causing transitions to fail with "Action N is invalid" when a ScriptRunner "Restrict transition" condition checks a field that the same transition's screen fills in. Atlassian has confirmed this is a defect in Jira Cloud: Forge workflow conditions are re-evaluated at execution time against the values just entered on the transition screen instead of the stored work item. It is tracked by Atlassian as https://jira.atlassian.com/browse/ECO-1851. The fix must come from Atlassian; we recommend watching and voting for that ticket. Only conditions that reference a field on the transition's screen are affected. Validators and post functions are not affected. We'll provide an update when Atlassian ships a fix. We apologise for any inconvenience caused and thank you for your patience.