I am running a tobit regression to model education expenditures (zero forsome households) and tried using margins, eydx(*) to obtain the elasticity estimates, but I got a r(459) error saying "could not calculate numerical derivatives -- discontinuous region with missing values encountered".

Could someone advise why this might be and how to resolve this?
Some details about the data I am using: my explanatory variables are mostly categorical variables, and the sample size is 300,000+ of which 240,000 are left censored.