I have noticed a very minor bug in sbcssm.F90 L.225 :
zcoef = REAL( nn_fsbc - 1, wp ) / zf_sbc
should be :
zcoef = REAL( nn_fsbc - 1, wp ) / ( zf_sbc - 1)
Changing the frequency of call to SI³ is very rare and the error only affects the first time step, however, for the sake of robustness, better to fix it at some point.