Licensee video of the issue here - [Link Removed]
This can be worked around with this setting: [Link Removed]
However it is not a solution as this setting actually causes other programs, e.g. slack, to artefact and there is a noticeable slowdown with various window launches.
Another strange thing to note is that this is only visible on the monitor, a screenshot actually picks up the correct window, the blackout is an overlay only visible on a monitor (occurs in 4.27 and in 5.0.3):
This is kind of non-deterministic but repro steps:
2.Open level blueprint
3.Right click across the graph page to repeatedly open a new context window over and over, varying the speed.
4.Eventually the window will blackout and will not return no matter how many times you right click again.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-156097 in the post.