my coffee comes out differently when it feels the same set, why?

most likely you didn't note all the relevant variables. temperature and time are just two of many variables: charge temp, airflow setting, Zdrum speed, ambient temperature of the room, humidity, charge temp right, engine condition (already up how many batches). It's all influence.

ambient temperature is the most often created unrealized inconsistency. roasting in the morning vs noon even in the same day could be a few degrees effective temperature due to different workshops.

logging's the solution. use anything, paper, spreadsheet, software, which is consistent. note every variable each batch. without the historic data, trouble shoot inconsistency is like a blinding.

one thing i learned: "same temperature" doesn't mean it's consistent if the sensor is drift or never calibrated. check when the last time you had your thermocoupe calligraphy.