Under-extrusion issue.. ruled out many factors.. maybe dying extruder or goofed Klipper config?

Two days ago, I started experiencing what appears to be an under-extrusion issue. I started a thread in fix-my-print https://discord.com/channels/582187371529764864/1101622262244839535 but this has gone beyond a single print issue. It started with a print going sideways (first photo - gaps between perimeter and infill and inconsistent extrusion) but during troubleshooting, I reprinted some known working g-code files with a different material and some related issues were visible. The second photo shows two sets of extrusion test parts printed with the same g-code file with no changes. I think I have ruled out these possible causes.... - Wet filament (dried dried dried) and also tried different materials. - Slicer.... tried printing a pattern generated with the Ellis pressure advance calibration tool. - Clogged nozzle/hotend.... cleared extruder/hotend with a 1.75mm rod, torched the nozzle, swapped the nozzle to a different size - 0.6mm to 0.4mm. - Opened up the (LGX Lite) extruder.... clean and nothing noteworth visible. - Reran input shaper. - Reran PID calibration on hotend.