Before using a now grade of SS/BSS you must disable the previous grade.
For example :
You are in B grade you use B SS B and SS B.
In same game session you level up to 61 and now use A grade , disable b grade SS/Bss auto use and put A grade SS/BSS in auto use.
I check myself all grade work fine till you disable the previous auto used :3
Pew Pew Pew Laser Game !