I have been running crossed random effects mixed models and the syntax that has always worked before (but which I had not used since January) has stopped working for me. The data set involves survey data with countries and years cross-nested. The basic model specification I have used is (here without any predictors for simplicity):

mixed dem_sat || _all: R.year || country:

But where this command was working for me in January, now I get the following output:

MapRowsToIntegers(): 3203 <tmp>[1,306293] found where colvector required
GenGroupSampleNumeric(): - function returned error
<istmt>: - function returned error
r(3203);

That happens no matter what dependent variable I use. I am running stata 16.1.