three body decay compilation error

Hello,

I have been implementing an extension of the Standard Model where a heavy colored fermion decays to a top and two Higgses. In order to implement this model, I copied the usrmod_v4 directory and added the following lines to particles.dat and interactions.dat:

particles.dat:

f f~ F S FMASS FWIDTH T f 300001

interactions.dat:

f t h h GWH GWH QED QED
f f g GG QCD

I then ran the ConversionScript.pl and left the new couplings GWH to their default value of 1. I then set the mass of f to 800GeV in the param_card.dat and add the following line in the f decay block

       1.00000000E-00 3 6 25 25

MadGraph5_v1_5_1 has no problem generating the process p p > f f~, f > t h h. However, when I try to generate events, I get the following error message :

Error detected in "calculate_decay_widths run_01"
write debug file /a/thserv01/g.theory/wilco/soniaeh/MadGraph5_v1_5_1/test_thh/run_01_tag_1_debug.log
If you need help with this issue please contact us on https://answers.launchpad.net/madgraph5
MadGraph5Error : A compilation Error occurs when trying to compile /a/thserv01/g.theory/wilco/soniaeh/MadGraph5_v1_5_1/test_thh/SubProcesses/P0_f_thh.
 The compilation fails with the following output message:
     gfortran -O -w -ffixed-line-length-132 -w -c -o symmetry.o symmetry.f
     touch qmass.inc
     gfortran -O -w -ffixed-line-length-132 -w -c -o cuts.o cuts.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o cluster.o cluster.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o myamp.o myamp.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o genps.o genps.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o initcluster.o initcluster.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o setscales.o setscales.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o reweight.o reweight.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o get_color.o get_color.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o matrix.o matrix.f
     gfortran -O -w -ffixed-line-length-132 -w -c -o setcuts.o setcuts.f
     gfortran -O -w -ffixed-line-length-132 -w -o gensym symmetry.o setcuts.o cuts.o cluster.o myamp.o genps.o initcluster.o setscales.o reweight.o get_color.o matrix.o -L../../lib/ -ldhelas -ldsample -lmodel -lgeneric -lpdf -lcernlib
     matrix.o: In function `matrix_':
     matrix.f:(.text+0x104): undefined reference to `iossxx_'
     collect2: ld returned 1 exit status
     make: *** [gensym] Error 1

For processes such as p p > f f~, the event generation works fine. Is there some specific problem related to the 3-body decays?

Best,
Sonia