when i started with mach3 i also found this rather unusual , that the machine wouldnt return to the point where i stopped it

but when you start to read G code and start to understand what i means, then it all starts to make sense

for example , when cutting an arc ( as mentioned ) and you stop the machine lets say 1/4 of the way thru the arc , when you restart , it will not resume from that 1/4 point thru the arc ... it will either start at the beginning of the arc , or the next line of G-code

the same with height, z - axis ... if im doing a cut , stop mid way thru and then RAISE the machine ... when i restart , the machine doesnt know that it been raised , and will only change the height when a line of gcode tells it to , so you may do an air cut for a few lines of code depending on what you cutting ....

if i stop and want to continue , i rewind a couple lines of code ...

and yes , you need to start the spindle manually ( again g code tells spindle to start right at the beginning of the code )

keep at it and it all starts to make sense .... :)