Problems with repeated execution of Dynare 4

Dear all,
I am currently performing an optimal policy exercise, I am doing gridsearches with Dynare at the moment. The gridsearch changes the parameters of an interest rate rule which do not affect the steady state. At run 3367, I receive the following error message:

??? Error using ==> print_info
MJDGGES returns the following error code18

Error in ==> check at 43
print_info(info);

Error in ==> gsngiac at 295
check;

Error in ==> dynare at 68
evalin(‘base’,fname) ;
Error in ==> gridsearchm2 at 29
dynare gsngiac;

I encountered the same problem previously and was told that this means that the 18th eigenvalue can not be computed. It was suggested that I insert numerical values into the initval bloc rather than having dynare compute the initial/steady state values each time. I have done that but it still does not work. Strangely, if I enter the policy rule coefficients associated with run 3367 manually, rather than having them uploaded from the matlab file with does the gridsearch, it works!
I am very puzzled about this and wonder whether you guys have had similar experiences while gridsearching.
Best,
Ansgar