Hello:
I do not know if this is correct since I just started working with this kind of models and Dynare in general, however, i was having the same difficulty so I rewrote the gap equation. Now, Dynare solves for the same steady state IRIS does, but now I am having problems with estimating the parameters. Hope this helps you.
Regards
LMGZ
MVFIMF.mod (2.81 KB)