Drip Coffee Maker. Slow and then extremely fast Let me preface by saying I clean my machine every day. I only use filtered water.
Machine: Morphy Richards Fresco (Standard drip-coffee)
I use coffee grounds (medium roast). I don't know the grind. I buy the grounds from a local coffee shop.
When I make four cups (max capacity). basically filling the grind in the metal filer to &quot;4-cups&quot; mark (max).
, 3/4 of the way: The coffee pours at a reasonable rate till it becomes extremely slow. Only drops are coming out. Then finally like a pressure cooker, the coffee pours out a rapid rate. It has a sort-of burned smell to it. The coffee still tastes good.
The same does not happen when I fill the filter for 3 cups.
I find the 3-cup brew slightly less bitter, it has greater natural sweetness.
I can not tell why.
UPDATE: I found that this was much more prominent in my coffee which had chicory.
Not sure if you'll be able to get a definitive answer on this one, but to me it sounds like filter/coffee choking, and then somehow un-choking. This is something I've experienced with pour-over brews. I've used my Fellow Stagg [X] Dripper before, and at 15g of coffee it's perfect, however at 24g the weight of the coffee is too great and it presses the filter and coffee directly against the holes on the bottom of the dripper.

Throughout the process I'll give the coffee a few stirs with a stir-stick, and it will immediately start flowing faster. It makes sense that you'd get a sweeter more balanced cup when the coffee doesn't choke. To me it also makes sense that you have a greater chance of it choking with more beans. Not sure how it could un-choke by itself, one theory is that once enough water pressure is present it creates a low-resistance channel where water flows through very quickly (and this water doesn't extract much coffee, rather would mostly dilute in this case).