If you’re responding to a key event, i.e. OnKeyDown, inside a User Widget in blueprint and then attempt to use ‘Capture Mouse’ as part of the event reply, you will crash due to an attempt to dereference a null pointer (specifically a non-existent mouse event).
I was able to reproduce this issue on our end. I have written up a report and I have submitted it to the developers for further consideration. I have provided a link to the public tracker. Please feel free to use the link provided for future updates.
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