Yes, I provided five different categories.
For example, under the category of “misunderstanding”, an applicant thought that children who were not in her custody didn't need to be listed, when that is obviously not the case.
The second category is “failure to update an application”. For example, an applicant informed immigration that she had a child after she had submitted her application, and this child was barred for the rest of this sponsor's lifetime from being sponsored.
“Fear of exposure” is the third category. A number of examples can be brought to light here. An applicant feared telling her second husband about children from her first marriage, and therefore she did not include them in her application when she was coming over with her husband. Second, some people don't want to reveal the existence of children, for example, from extramarital relationships for fear that the interpreter or the consular office officials in their local community could share confidential information, or a person fears the reveal of a child as a result of rape.
The second last category is “lack of knowledge or bad advice”. This is obviously bad advice given by a person in a community or by a lawyer.
The last one is “unaware a child was existing at the time”. One tragic story is that a woman came and didn't know that her children were still alive. The International Red Cross had identified them, and they notified her that they had found her children after some time, but our immigration rules still prevented her from being reunited with her children.