so managed to do a bit more work towards finding the culprit and had some disappointing results.
while I was at it I upgraded to OS 5.9 just to see if that would work by itself, but alas that did not do the trick.
next I reduced the volume in my config to 1500 and again no joy.
I did as you suggested @ForceMantle and replaced the swingh, swingl and swing files to see if that would work. (I swapped them out each file one by one and then all of them together)
i even swapped the hum file to see if that would help.
now I swapped them with a font I know works even at low voltage from the battery and I’m still getting some distortion.
it is a bit less than what I was getting from the TFA GRAFLEX font.
so I’m totally confused now.
could this maybe have something to do with my config setup?
its just plain weird that this is the only blade/font on my config to be suffering from this.
I did have a look at the sound files in audacity and all the swing files are just under the 0dB limit, and I think this is normal from my recollection.
@profezzorn, the 5v external supply, could this be done by plugging in a usb while the board is on?
would this supply the 5v needed to check the switch mode for operation?