Hi. My name is*****'m a camera repair technician with over 20years in the business and I'll be glad to help you with your question today.
This is usually caused by a faulty AF motor. These have a tendency to go bad more often than they should. The good news is the lens is very repairable and, with a little shopping, can be repaired inexpensively. You may want to check locally for a camera repair shop in your area, or, if you need assistance finding a shop, please let me know and I'll locate one for you.
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