Sorted out the nesting subroutines - I cut a row of parts along a sheet, step up, rotate 180deg & cut a row back.
HOWEVER
The part has holes in it cut using incremental subroutines. When cutting at 180 deg, the lead in (G1) cuts in the correct direction but the arc (G2) is upside down - a J5 puts the arc centre 5mm above the start point whatever the rotation.
Why are I's & J's after a G91 not affected by a G68?
Any explanations?