No, it never was really in arranger mode, in my test I only enter the arranger menu and arranger editor and then exit them, the arranger mode led never turns on.
No, in arranger mode it’s not a problem because the counter is supposed to be printed in arranger mode, and instead of printing “-:-:-” it prints “1:1:1”.
Moreover, if I enter and immediately exit arranger mode, and then follow the steps to reproduce the problem, instead of printing “-:-:-” it prints “1:1:1”, as if some arranger state had been initialized. If in MKI you have to be in arranger mode to enter the editor, it might affect only MKII.