RE: Threads don't work, not sure where to start troubleshooting
When you mention "varied extrusion from 90 to 100 via firmware" are you talking about Flow Factor from within the Tune menu when the printer is printing ?
If so I think I remember reading somewhere that this is different to extrusion multiplier inside PrusaSlicer (maybe I'm talking rubbish here 😀 )
As an example I've got a filament saved as a preset and the Extrusion Multiplier is set to 1.0732 and diameter of 1.7539 (after tuning) and I never change the Flow Factor.
RE: Threads don't work, not sure where to start troubleshooting
Yes I do mean the flow factor.
My understanding is that slicer sets the flow factor to 95% and then the extrusion can be set per-filament but they both affect the same thing. If that's wrong I guess I need to re-slice and do some more testing.
I found the reference: https://help.prusa3d.com/en/article/extrusion-multiplier-calibration_2257/
The Extrusion Multiplier allows the fine-tuning of the extrusion flow rate - simply described as how much filament comes out of the nozzle. In other words, the Extrusion Multiplier setting in PrusaSlicer and the Flow rate setting in printer firmware are two ways to adjust the same thing, however, adjusting one of those two settings will not influence the value of the other.