Sorry for the bump
I’ve been having this same issue, I have found it may be related to controller support within the editor, occasionally the editor seems to receive an input from the controller on the left stick despite not having any before (most likely due to floating point inaccuracy stacking up).
The stick was continually moving from the viewport of blueprints to the components tab, I flicked the stick to reset the axis to 0 and my delete key worked again.
I am hesitant to mark this as an answer, but it might be worth trying, if anyone else experiences this issue.