Good news on the clean machine. I wasn't suggesting yours was not, only that a poorly maintained machine would lead to such flavors, which has me scratching my head a bit.

I gathered that would not have been the case. Have you opened up the Niche to verify the center bolt is tight and that everything is in order on that end? Suddenly needing to grind much coarser coupled with poor tasting coffee is quite the coincidence.

90°C is quite a cool brewing temperature. Are you brewing quite dark roasts? If not, have you tried brewing at 93 or 94°C?

Cheers!

- Jake

Jake_G wrote:
The change in grind setting is a really interesting phenomenon. !

- Jake

That's a thing, I was surprised too.

When I switched from a WAC to a SAC softening setup my grind size changed noticeably with the exact to same batch of coffee to maintain the same extraction time.