There is nothing wrong with your model. This is a consequence of how Apollo works.
In Apollo, you usually define random components as follows:
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randCoeff[["beta"]] = mu + sigma*draws
Now, if after estimating you model, you try calculating the likelihood (LL) of your model with your estimated parameters, but changing the sign of sigma (e.g. from negative to positive) you should get a very similar LL that the optimal LL. It will not be exactly the same because "draws" is not an ideal probability distribution, but instead a set of draws from the desired distribution. These draws are almost never perfectly symmetrical around zero, which explains the difference.
But in summary, negative s.d. are nothing to worry about. You can read a bit more about it in the F.A.Q.
Best wishes
David