Sounds like one guy's opinion, not gospel.

Checked the return air path first before touching the refrigerant, and that saved me. Had the same thing happen at a pizza place, box of dough pushed right up against the coil, air couldn't move, temp went crazy. Pulled the box back, gave it about a foot of clearance, and the swing went away in an hour. Now I walk the whole box before I even break out the gauges. Learned that lesson the hard way after a long night of looking like a fool. Clear airflow solves most of these calls.

That bit about the barista saying dark roast "hides the flavor of bad beans" is real and it saved me a ton of money once I figured it out. I did the same thing for years, buying the darkest, oiliest bag on the shelf because I thought darker meant more caffeine. Turns out it's the opposite, dark roasting burns off some of the caffeine and just leaves you with that ashy taste. One thing to watch out for now that you're into medium roasts, check the roast date on the bag instead of the expiration date. Anything over a month old has already lost most of those cherry and chocolate notes you're tasting. Also don't sleep on light roasts for your pour over, they can be even fruitier if the beans are good. Grocery store beans are usually the problem, not you, since they sit on shelves forever.