1995 Rheem tripping 40A breaker
Well, from the name plate the max breaker size is 35 so that is the size breaker it should be on.

It is possible the breaker is going bad. Especially if it only trips occasionally and not immediately every time the compressor starts.

It is also possible the unit is going bad and only occasionally draws more than its rating. When the technician was there it just happened to be acting normally.

The cheapest fix is to try a new 35 amp breaker. If it continues to trip then you need to call the HVAC contractor back out for a more thorough examination.

Good luck!