anchor.diff:  C
   C A1. WHEN THERE IS NO TRACKIING THROUGH THIS ELEMENT
   C
  -CMWF PYADH HAD            IF(DABS(D1).LT.DN_SAFE)THEN
  -            IF(DABS(D1*DL).LT.ZEROTOL)THEN
  +            IF(DABS(D1).LT.DN_SAFE)THEN
  +C            IF(DABS(D1*DL).LT.ZEROTOL)THEN
                  IF (IDEBUG.GT.0) THEN
   C MWF DEBUG
                     WRITE(6,*)' ELTRAK CASE A1 D1= ',D1,' D2= ',D2,
  
positive.code:       ELSE
           TERM4 = (SE - (1.D0 + S + 0.5*S**2 + ONESIXTH*S**3))/(VX**4)
        ENDIF
        IF (SMAG.LT.(120.D0*ZEROTOL)*(0.2D0)) THEN
           TERM5 = DT**(3.D0)*(ONESIXTH + ONE24*S)
        ELSE
           TERM5 = (SE - (1.D0 + S + 0.5*S*S))/(VX**3)
  
negative.code:             WRITE(6,*)'ELTRAK AFTER 150 DN(',I,')= ',DN(I),
       &           ' DABS(DN*DL) < ZEROTOL= ',DABS(DN(I)*DL).LT.ZEROTOL
           ENDIF
  C PYADH HAD
  C         IF(DABS(DN(I)).LT.DN_SAFE)THEN
  C            CALL DN_CHECK
  C     I           (MAXND,NODE,NEQ, 1.D0,DN_SAFE,
  C     I           DN,
  C     O           I1,I2,I3)
  C LATER VERSION WAS
  C         IF(DABS(DN(I)*DL).LT.ZEROTOL)THEN
  C            CALL DN_CHECKA
  C     I           (MAXND,NODE,NEQ, DL,ZEROTOL,
  C     I           DN,
  C     O           I1,I2,I3)
           IF(DABS(DN(I)*DL).LT.ZEROTOL)THEN
  