Yes, it's possible. People can be below proficient in the "Initiation" or the "Closing" or the "Professional and Social Responsibility" domain and still pass the PMP exam. It is also possible for some (lucky) candidates to be below proficient in more than one of these domain, and still pass.
However, applicants scoring below proficient in the "Executing" domain, for example, will almost certainly fail.
The reason why it's possible for people to fail in certain domains and still pass, is the grading structure of the PMP, and the grade share attributed to each and every domain:
Initiation: 11% of the total grade
Planning: 23% of the total grade
Executing: 27% of the total grade
Monitoring and Controlling: 21% of the total grade
Professional and Social Responsibility: 9%