Engine Noise problems of the 2007 Chrysler 300C

The vehicle has had two owners in the same family and has very low mileage (66000). The issue began in October of 2018. While driving on city streets at 40 mph the indicators on the dash began flickering and making noise. This continued intermittently for three months but could not be replicated at an independent mechanic. Then in January of 2019 while driving on the freeway at 65 mph the same issue happened except this time there the speedometer went to 0 but the car could still be operated. The car was taken into an independent mechanic who attempted to diagnose the issue for over a month but had no luck. As instructed by the mechanic the car was brought to the dealership where it was purchased brand new in 2006. The dealership kept the car for 6 days in February of 2019 and could not diagnose the issue, charging the owner a $240 fee for nothing. As soon as the owner left the dealership the car again experienced the same issue while driving on the freeway. The car was brought immediately to the owners personal mechanic who has had the car ever since. The mechanic has since brought the car to another Dodge/Chrysler dealership in town who charged an additional $600 ending in no diagnosis. The car is unable to pass smog as now the problem occurs more frequently and is unsafe to drive. I have seen this complaint several times online and it would seem to me that Chrysler should be responsible for fixing or compensating the owners for an obvious mechanical issue.