This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
Creating multiple levels at one time will cause the editor to freeze and lock up and may lead to an "out of memory" crash in the editor.
1. Download and unzip attached project
2. Open the project and click Create Levels button in main editor toolbar.
Result:
Levels will continue to be created until editor stops responding and leads to an OutOfMemory crash.
Head over to the existing Questions & Answers thread and let us know what's up.