Same thing happening here… And yes it is related to AI assistance for ATC to be on. When this assistance is set to off, the pushback is not automaticaly triggered. When set to on, the automatic pushback is asked by “co-pilot” somewhere just after engine is prepared to be started, usualy just before APU set to be switched on, and/or after you switch on the bateries. Turn off the assistance or be quick with canceling the pushback request 
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