Settings first or hardware first when prints go weird?

Funny, my two week saga went the opposite direction on hardware. Mine was an Ender 3 V2 and the prints slowly got more and more gappy over about a month. I blamed my flow rate, retraction, humidity in the garage, all of it. Turned out the little plastic lever on the stock extruder had a hairline crack in it, so the spring tension was slowly fading. Every tweak I made to the profile was me compensating for a part that was basially failing in slow motion. Swapped in a metal one and it was like a new machine.

On my Ender 5 Plus the sneaky culprit was the Bowden tube not seating flush against the nozzle. Little gaps form down there when the nozzle loosens slightly over time, molten filament backs up into the gap, and slowly the flow just gets worse and worse. I wasted most of a weekend on flow calibration because every test cube looked slightly different and I kept chasing numbers. Once I pushed the tube down properly and tightened everything hot, the problem was gone in one print. So my answer to your question is that I do a fixed visual pass now before I touch a single setting. Torch around the hotend, check the tube coupling, pull the filament and look at the tip, spin the extruder gear and watch for grind marks. Maybe fifteen minutes of looking before I even open the slicer.

I get why settings feel like the likely culprit, they are the stuff we can actually control, but on these machines the things that fail are mostly mechanical and mostly cheap. A profile does not drift over time, hardware does. The tube seat thing especially, because it creeps in over weeks and everything still prints, just badly, which is exactly what pushes people toward endless tweaks.

Cold pulls are worth learning too. Mine would have saved me that weekend if I had bothered.

Mine ended up being a cheap inspection camera off a marketplace listing, like the little ones that plug into your phone. I'd been eyeballing the hotend with a torch and thinking it looked fine, but once I could actually see up in there the filament path was half blocked with dust and old burnt filament. Cleaned it out with a brass brush and the problem I'd spent a whole month blaming on my bed leveling just vanished. Now the camera lives in the printer drawer and comes out before I touch a single setting. wierd how the cheap fix for looking was the last thing I thought to buy.

Reading this as someone three weeks into owning my first printer and I feel a bit seen. My instinct has been the total reverse of yours, I stripped the whole thing down looking for a hardware fault before even opening the settings. Turned out my underextrusion-ish mess was just the filament diameter left on the default after I swapped spools to a diferent brand. Changed one number and it printed fine. So now I've got no idea what the sensible checking order even is. Is there a list somewhere that goes easiest check to hardest? I'd love to stop guessing.

Update: fixed, and annoyingly it was my own stubbornness. After reading about the Bowden tube backing up I pulled the nozzle again and checked the tube seat properly, sure enugh it wasn't flush and there was old filament packed into the gap underneath. Trimmed it square, reseated it, new nozzle in, and the last three prints have come out clean. Also ordered one of those little camera things after seeing that reply, clearly eyeballing it from the side wasn't cutting it.