Error opening KiCad generated Excellon files for drilling

[LMS71]

I had problems trying to open an Excellon file generated in KiCad v8.0.1, FlatCAM (beta_8.994_x64) complains that "it is probably not an Excellon file".
Various iterations of the KiCad Excellon settings under the Plot > Drill Files options were tried without success (i.e. mm/inch, relative/absolute etc.).

On closer inspection of the KiCad generated .drl file, it was noted that there seemed to be two extra tools defined (whereas the PCB only has holes of all the same size - 0.8mm).

Example from the file, T1 and T2 are not in the KiCad PCB.
; #@! TA.AperFunction,Plated,PTH,ComponentDrill T1C0.000 ; #@! TA.AperFunction,Plated,PTH,ComponentDrill T2C0.001 ; #@! TA.AperFunction,Plated,PTH,ViaDrill T3C0.800 ; #@! TA.AperFunction,Plated,PTH,ComponentDrill T4C0.800

Deletion of T1 and T2 resulted in the file being opened in FlatCAM with no further issues. I suspect the zero diameter tool is the problem.

For clarity I also merged T3 and T4 into one tool.