I am attempting to run a multilevel beta binomial model (with multiple imputation) and am getting some warnings from Stan. Are these safe to ignore or could I avoid them with better priors or starting values or something? Thanks!

```
m <- brm_multiple(
formula = y | trials(27) ~ 1 + x + w + z + (1 + x + w + z | cluster),
family = beta_binomial(link = "logit", link_phi = "log"),
prior = set_prior("normal(0, 2)", class = "b"),
data = mids,
backend = "rstan",
...
)
```

Messages from Stan:

Chain 1: Rejecting initial value:

Chain 1: Error evaluating the log probability at the initial value.

Chain 1: Exception: beta_binomial_lpmf: Second prior sample size parameter is 0, but must be positive finite! (in ‘string’, line 141, column 6 to column 85)

Chain 1: Exception: model51c034f86857__namespace::write_array: y is not positive definite. (in ‘string’, line 152, column 2 to column 66)