Same thing happened to me with vinyl. I kept blaming my technique and then finally swapped the blade and it was like night and day. Now I just swap every few weeks instead of trying to squeeze every last cut out of one blade.

Man, a butter knife fix that lasts 4 months is a WIN in my book. My old toaster had a lever that stopped latching so I just wedged a folded up matchbook under it and that thing ran another year. Sometimes the cheap fix beats shipping it back and waiting on a replacement. You saved yourself a whole headache there.

Question whether a gram of magnesium is actually a big deal since plenty of people take that much on purpose for constipation or muscle stuff. Five days of stomach issues sounds more like your gut just adjusting than some scary overdose, and cutting back probably helped because you changed something, not because 500mg was dangerous. The dose on the label is a serving size suggestion, not a hard limit, so maybe relax a little.