When and where did you purchase the 6HC?
Is this a new build? Has it ever worked correctly?

Can you send M122 and M98 P"config.g" in the gcode console of DWC and copy and paste the results here?

@darylprice post your full config.g

Try prusa slicer as a sanity check?

How fast are you extruding into free air when you're testing? Are you actually matching the feed rates that would be used during the print?

The only difference between the walls and infill is the extrusion width. Though the volumetric flow is lower on the walls than infill due to being slower.

That still may be too high for TPU. Try dropping the print speed by half.

TPU is hard to print with to begin with. Testing with PLA would be my next step.

When was the last time prints were working correctly?

I doubt it's a firmware issue, but it could be related to your configuration. 16x microstepping is the norm. If your steps per mm are way out of whack for 1x microstepping no wonder things aren't extruding well.

The sliced gcode file you shared shows nothing out of the ordinary when previewed in prusa slicer gcode viewer.

Why 1x micro stepping?

Have you tried with pla instead of tpu?

@droftarts it won't run i'm afraid as it only has 512kb flash. not enough to fit RRF into (we're at about 730kb without the bootloader (another 32kb))

@Handymanpa54 start a new thread please and add in as much info as possible e.g. config, board. Firmware version

Try reslicing the file with the same speed for walls and infills.

; Extruders
M584 E0.0 ; set extruder mapping
M350 E1 I1 ; configure microstepping with interpolation
M906 E1100 ; set extruder driver currents
M92 E562 ; configure steps per mm
M566 E3000 ; set maximum instantaneous speed changes (mm/min)
M203 E12000 ; set maximum speeds (mm/min)
M201 E5000 ; set accelerations (mm/s^2)

This is a very strange extruder setup. What kind of extruder is this?

Are you able to extrude in free air from the DWC extrusion commands?