Checked on raspberry forums and it seems there is no other way - just update. Probably bootcode.bin from piCore 6.0-SSH is not compatible with current revision of B+.
By the way, my tcz that was compiled/created on 6.0 still works on 8.0. I created sin...
By the way, my tcz that was compiled/created on 6.0 still works on 8.0. I created sin...