Summary

Cannot choose a parent when bulk converting a huge number of issues into sub-tasks.

Steps to Reproduce

1. Create 500 issues in a project
2. Do a JQL on the 500 issues and initiate the bulk update
3. Choose the move operation and switch the issues to sub-tasks
4. Click on the Parent issue drop down

Expected Results

The list of possible parent issues should be displayed

Actual Results

The Parent drop down fails with 400 error and the message.

The Jira server was contacted but has returned an error response. We are unsure of the result of this operation.

Workaround

Split the issues using the JQL and bulk convert the issues in smaller batches.