Running the above code illustrates this common situation.
The output shows some of these problems

OBS  ID  LASTNAME    DOB    HEIGHT   WEIGHT   GENDER   AGE
  
 1    1  SMITH         .      68       144      M       26  
 2    2  JONES         .      78       202      M       32  
 3    3  DOE           .      62        99      F       45  
 4    4  WASHINGT      .      66       101      F       22

Notice that LASTNAME is truncated and DOB has all missing values.