I'm sorry to hear of your difficulty coming back. I just read of the decrease in prednisone - perhaps a slower taper would reduce the symptoms? It is at least a question for the doc.
As a person with asthma/bronchiectasis, I will tell you that breathing issues are a daily mystery. For example, yesterday afternoon, I was sitting on the patio, playing a game with friends, and suddenly could barely catch my breath - an hour later, walking home, I was just fine. I know from experience that a rescue inhaler might have helped, and a check of my O2 sats would have shown them to be above 90%. The pulmonologist has no explanation either.
I have a friend who is 7 years post-chemo, post-radiation for throat & thyroid cancer - she had a feeding tube for about 4 years before she was able to transition to a liquid diet, and even now, she must be extremely careful about aspiration. Another acquaintance was never able to change, has always had to use a feeding tube. I don't think that part of your situation is uncommon.
The human body is an amazing and complex organism, and the more doctors and scientists learn about it, the more mysteries they find.
Sue

@thomason Oh, dear I don't know how to answer your questions. I've asked the same. My Oncologist said that medicine is a blunt instrument. Not perfect.

I had to have a dose of cortisone in a knee that was acting u late afternoon. I have a low-grade fever, headache and I sweat all night long after just changing the sheets.