Okay, so ever since UE4.25 released, this issue no longer occurs, which is nice.
However, between the time I originally posted the question and now, I did come up with a “solution” (although it is a pain to work around). So in case anyone happens to come across this same issue in the current UE4 version or future versions, here is what I did.
Basically you had to select all the keyframes of the pose morph, right-click, and select “Auto”
Then apply and save changes. The pose morph keyframes should now be working fine. If “Auto” doesn’t work, try “Linear” or “Constant.” Unfortunately, this solution is very tedious as you’ll have to do this for all the pose morph keyframes. Like I said, UE4.25 fixed this issue for me so I no longer have to do it, so hopefully this will not be an issue for anyone else. But in case there is, I wanted to put this solution out there so no one had to be stranded for answers like I was.