If a brew is put in a brewing stand to distill, then while the it is distilling, is replaced with another brew (does not matter what the replacement is, trash brews work just fine) via hoppers (so the replacement is immediate) it does not interrupt the brewing process and the distilled brew will be the result as if the original brew was properly distilled.

Example:
Berry Brew will give Sweet Berry Crush.
While it was distilling it was replaced with Muddy Brew which should yield indefinite distillate
It instead gave the Sweet Berry Crush and the player still has the original Berry Brews to repeat the process.

what was the muddy Brew intended to be? MAy be an update bugg thing

We tested it by brewing with just 1 item (sugar in this case). Fermented 1 piece of sugar, bottled it and could use that brew to replace others as seen above.

The muddy brew was from the original player reporting it. I'm actually not sure what they brewed into that one. But we managed to replicate it with others.

Update: The Muddy brew is just what they got when they added something to the cauldron and immediately bottled it so they could test the bug. It was just one item added to a cauldron and should not have ever resulted in a brew.

Thank you for your detailed description. I'll try to figure out why this is happening!

Sorry i thought i had replied to this. I could not reproduce this issue, anything i tried, even with hoppers and stuff i could not make it happen.

Try in v3.0, as some code with the Distiller has been changed.