It turns out that the issue are the square brackets. Once I replace them with strcat, everything works perfectly now.
Before:
AA = [AA, 'Cruise #', num2str(cruiseList(i)), ', Year: ', ...
Sta{Ind1}.year, ', Month: ', Sta{Ind1}.month, '.'];
After:
AA = strcat(AA, 'Cruise #', num2str(cruiseList(i)), ', Year: ', ...
Sta{Ind1}.year, ', Month: ', Sta{Ind1}.month, '.');