I grow weary of this bolt

After +Tim Hatch's suggestion started making more and more sense, I re-soldered the Z and E microstepper jumpers. After that, it's time to recalibrate - I might have thrown all the microstepping off.

First with current settings, extruding 50mm at 220C, 25mm/min, 16 microsteps, fudge factor 50/90. Extruded roughly 5mm.

Removing fudge factor, extruding 50mm. No movement of filament. Seriously? Stripped again? Taking it apart and doing a cold pull. Bolt doesn't look stripped.

Extruding 5 mm looked fine. Extruding 50mm extruded 41mm. Applying that as fudge factor.

Extruding 100mm extruded ... nothing. Once again forgot to make the fudge factor a float.

Extruding 100mm again got 42.1 mm. This is freaking random. The gears move correctly, but little comes out.

Maybe the hobbed bolt is worn down? Sounds unlikely, since it's supposedly high quality, and I haven't used it that much, but let's have a look:

When newly purchased

Current state

They actually do look worn - the thin parts that come in pairs are clearly worn at the ends, less clearly in the center, but still worn down enough to be below the bigger flat pieces. That would explain lack of traction without actual stripping.

This bolt was the Hyena 2.0 from arcol.hu. It lasted a bit over a year of intermittent use, and that was even the chrome-plated supposedly more durable kind. Dis-a-pointed! What's the best hobbed bolt these days? There's the Concentric from Airwolf3d, but I read that it's so wide and shallow that the filament tends to wander. Then there's the Hobb-Goblin from E3D, which is at least stainless steel, but the grooves look shallow. Various forum comments sound good, though.

There's a fairly comprehensive test on Instructables - not including the Hyena, alas. But they give pretty good grades to the Hobb-Goblin, so I'll get that. Only the RobotDigg were better, but the ones tested were different from the Wade's-compatible ones, and I don't see what material they're made from.