RETURN is used with GOSUB.
You will want GOTO CHECK

From the manual:
RETURN

Return from subroutine. RETURN resumes execution at the statement following the GOSUB which called the subroutine.

Gosub sub1 ' Go to subroutine labeled sub1
...
sub1: Serout 0,N2400,[“Lunch”] ' Send “Lunch” out Pin0 serially
RETURN ' Return to main program after Gosub