The machine has a look ahead function and reads ahead so it is seeing that error somwhere else
use the "Stoppre" command to make it look to the last line before going forward
Stoppre
$AC_TIMER[3]=0
WHENEVER $AC_TIMER[3]>=6 DO $AC_TIMER[3]=0
WHENEVER $AC_TIMER[3]<=2 DO S130
WHENEVER $AC_TIMER[3]>=4 DO S120
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N130 G1 Z50 F.1
N132 G1 Z49 F.06
N134 G1 X72 F.1
N135 $AC_TIMER[3]=-1
Stoppre
If the timer doesnt work increase or decrease by declaring the spindle speed as an "R" value and can be changes at random