May I dare to suggest that is the passengers who are not consistent.
As is their right, they tend to have adhoc requests, wish to engage in conversation, have problems for crew to sort, eat at different speeds, drink different amounts, have many different needs from the inflight experience etc.
Unlike service routines which are written in offices and tested on willing watersiders, who sit and observe the script.
Passengers are human, not guinea pigs. Perhaps the problem is that the service is inflexible and does not take into account adhoc needs and problems, perhaps this is where extra hands on deck are a bonus.
The service works well when everything else works well, in all cabins. If all the equipment is working, if all the product is available and if passengers are in the mood to take just what is given then service can be consistent. However we all know the reality...
And maybe this is where some crew excel over others. Thinking outside the box and going the so called extra mile to make things work. An area of goodwill which has suffered under Walsh's civil war.