Been there man, it's always the cheap stuff that gets you. I spent weeks messing with my coal forge airflow, adjusting the tuyere and messing with different fuel sizes, because my fire kept burning cold on one side. Turned out the grate under the firepot had warped just enough that ash was piling up uneven and choking half the air. Ten dollar piece of steel and I was chasing ghosts for a month. You're right that you just stare at the failing part and never think to look upstream. Glad you got it sorted for six bucks, that's a win no matter how dumb it felt.

Funny you bring this up because for years I figured anything that cheap was a waste of time and I'd just touch up the edges after. Then a guy showed me how he tapes foam pipe insulation over door edges and I felt like an idiot for all the hours I spent chasing chips. Now I keep a whole bin of that stuff plus cheap chip brushes and acid brushes for seam sealer. None of it costs more than a few bucks and it saves way more time than it costs.