Hi, I just now had the same problem, I think this is whats happening: you put clips into one sequence and then you put that sequence into another sequence, everything is fine for now, until you reverse the sequence, but you see black because premiere sequences aren’t just your clips, the BLACK NOTHINGNESS after the clips is also a part of the sequence, so what happened is your reversed sequence is showing you the endless darkens before it shows you your reversed clips
the trick here is to NEST (select all clips and right click and select the nest option) the sequence you wish to reverse, this will create a nested sequence, just use that one as a clip and reverse and speed up as you wish ,
worked for me 😀