The following steps can reproduce the crash detailed in issue UE-51922:
- Prepare a UI with 2 comboboxes vertically next to each other, and multiple elements (5+) in the top box.
- Start the game in Standalone or Build
- Move the UI so that the Top Combobox is closer to the bottom edge of the screen than its dropdown’s height
- Click the top combobox → The Dropdown opens and touches the bottom edge of the screen / extends past it
- The Dropdown should be flickering between 2 positions. If this behavior is not present, the crash will not occur. Try moving the UI and to open the Combobox again.
- Click an Entry in the Dropdown that overlaps the bottom Combobox
- Observe Crash.
As this issue is logged for the current versions of UE4, but no reproduction steps are given, I hope this report can help with resolving the issue.
My project uses Dropdowns quite extensively and modifying engine-code is not an option for me. If there’s any workaround/help you can offer despite that, I’d be delighted to hear it.