Been there. I grabbed a cheap bag for my kid's class cupcakes last spring and those things came out like hockey pucks, all sunk in the middle. The batter felt wrong too, kinda gritty and it never got that smooth ribbon look, you know? I ended up dumping a whole thing of sprinkles on top just to hide the sad tops. Old flour can also be the problem if it sat on the shelf too long, that stuff loses its punch. You probably did nothing wrong, sometimes the cheap bag just does not have enough protein to hold a cake up.

Yep, got quoted $850, driver showed up wanting $1400.

I had the same thing happen with a $6 gas station rag on my car windshield and ended up leaving half the pollen because it looked like a galaxy. Turns out the trick is stopping before the streak dries, thats when it turns ugly.