Hello, can you please tell more details about your issue? We want to find the exact problem.
If there are some other persons at your side facing the same problem?
If I want to find a person from phone book I click on contacts and in the search line to drive the first letters of the name of the desired person, then choose the contact, start calling, and that in such a situation, my proximity sensor is not working. We have lock button, then immediately release the lock on the same button, and then the proximity sensor starts working correctly.