Advice for a new (to the Bullet) coffee roaster - problems started after disaster struck

Hi everyone, I have been roasting on two Freshroast 540 and 800 / roasters for several years, typically doing 10 separate roasts with beans from 4 origins to create an espresso mix that my friends and family really enjoy. It was taking me hours so I decided to splash out on an Aillio Bullet.
After completing the 5 super dark seasoning roasts with my new machine using the Brazilian beans supplied, I roasted a batch of the Brazilian for consumption and it was delicious.
The next roast I did was a disaster, turns out the two grub screws that hold the drum motor to the shaft were never properly tightened and the drum stopped turning causing the 2lbs of beans I was roasting to burn. I was able to tighten the screws and start roasting again, but can’t produce any coffee worth drinking. It’s always grassy on the front and bitter on the finish if I do a medium or a darker roast. I have literally thrown multiple llbs of roasted beans in the trash and am loosing hope.
I have tried following and replaying the first roast I did, but can’t get anything worth drinking, I am wondering if when the beans burned they have tainted the drum?
I would really welcome any suggestions and/or advice at this point, I am about to give up and go back to my Freshroast roaster :frowning:
Thanks for any help you can offer, Mike E.

I doubt you tainted the drum. Can you post a link to your roast? Make sure you click on action->share roast to get a link.

Also, how does the weight loss compare to the roasts you liked with the Freshroast?

It might be time to clean the IBTS. When it’s dirty (like after lots of smoke, or just time), the preheat temp and ibts graph will be off by a fair amount.