My Mom's 06 Ranger made a rattling noise then when she stopped and looked under the truck she didnt…

My Mom's 06 Ranger made a rattling noise then when she stopped and looked under the truck she didnt see anything loose or hanging. She stopped on an incline then she tried to put it in reverse gear but it wouldnt go into that gear. She drove it home with no rattling and once home on level ground the transmission would shift into reverse. What would cause this? Two days earlier she had an alignment done at a shop. She suspects the mechanic did something to her truck to cause this. Shes had similar things happen with mechanics in her area before.

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