According to the maintenance manual, if i recall correctly, push to level off is not exactly a V/S zero mode, but an ALT mode. If this is correct you can use it for a while.
But you can just introduce a higher CRZ ALT, then initiate a climb, then inmediately go back to level, then ATL should come active.
And, let's not forget the golden rules. If the airplane is not doing what you want, and you don't like what the A/THR is doing, disconnect without fear.