If you change focus to the Blueprint Editor (Alt+tab) while a Microsoft IME keyboard is active, the editor will freeze for a short time. The duration of the freeze is dependent on the number of blueprints open and their complexity.
Note: This is specific to Windows 8 and 10. It does not occur in Windows 7. This also only occurs with the Blueprint Editor.
Regression?: No
This also occurred in 4.14
Head over to the existing Questions & Answers thread and let us know what's up.