Hi,
I have this problem in a Yang Lathe with a Fanuc O control,
the M01 optional stop is not working.
It only works if I program it directly after a M00, like this:
T0100
G97 S300 M3
M0
M1
M1
M1
M8
M30
If I remove the M00 the program ignores all the M1 and jumps directly to the M8.