Bean temperature stays behind

Hi all, im new in roasting, and just got my Bullet a month ago. I did about 10 roast so far, but my first one was the best, by far… I did this one just after the first 3 seasoning batches.
The smell of the coffee was delicious when it came out and the taste is great, almost perfect for me after leaving it for 2 weeks.

I used the same receipe now for the other roasts, but im not reaching the same results :frowning: The taste is flat / grassy / underdeveloped. From what I can see in the data, my bean temperature stays behind, while the IBTS is about the same. With my good roast, the BT goes closer the the IBTS to the end of the roast, but at my bad roast, it never seems to get closer. Does anyone know what could have caused that? And what can I change, to reach the same result as my first roast?

First roast:

The ‘failed’ roast, the fourth of doing back to back roasting: