I think posting an obvious UEInsight screenshot on this forum in a thread about UE’s performance should be sufficient to get the issue heard.
I wish I had your optimism, some of these issues have been in the engine since 5.0EA which was about 3 years ago and still not addressed :'D
Just to note, @skfabby same issue does indeed appear on 5.4.4 with the RHI Interrupt and RHI Submission Threads.
Reduction in FPS from ~90 down to 37.5. Entirely attributable to these threads operating asynchronously
It happens spontaneously but as an added trigger I have found calling Load Level from Blueprint can sometimes trigger the issue. The only fix is to completely close and restart the application.
You can see here 18.9ms of Game Thread doing nothing but waiting for RHI:
For context 18.9 ms is longer than an entire frame should take.