luckily/hopefully the new Mira will fix that problem.I can confirm that I had the same problems when trying to backport spiderman miles morales. I tried all "1-click tools" I found for automatic backporting but all gave me errors when installing or when trying to start the game. After x tries I gave up on backporting this on my own and used a backported fpkg from the www and it worked fine.
I didn't had this problem with other games I backported to 5.05 so I guess the game has something different what needs to be done the manual way.