Problem when sending file via ajax

I am trying to send a file via ajax but I get a 400 bad request error.
My code

data.coverQuestions.medicalMalpractice.file = docFile.prop('files')[0];

url: '/wp-admin/admin-ajax.php',
method: 'post',
data: {
  action: 'insurance_form_data',
contentType: false,
processData: false,
success (res){

If remove the parameters and do not send files, then in this case it is successfully sent.

contentType: false processData: false

What could be the problem?

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Author: Pavel