Most cabin crew are 1-2 short these days. Rumour has it an indefinite number resigned after the 13th month. How true I’m not certain but numerous are crewed by last minute call-outs.
Contract crew are paid very little and can’t see themselves coming to work on certain days.
Short of crew, certainly not. just ask the DFO.
As for manning the food cart, the ISM do what they are told, from ISD of course.