Thank you David, hopefully allowing high jerk for travel moves will resolve the issue.
I'll try and source a 3mm bowden tube. In the mean time I'll turn off the pressure advance feature for now. I just printed a floppy cleaning kit someone asked for but the filament lost traction for about 10 layers before picking it up again due to the extreme back and forth motion of the extruder motor, especially with narrow infills like 2-5mm wide.
Especially the turn tool got out with under extruded layers, it was easy to snap them in two parts. I've reprinted it without PA and came out fine.