g23 2020 v drive have noice and metal contamination

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my G23 2020 suddenly have some noice in the v drive when forwarding and backward... when we check the v drive fluid.. the colour of the oil change to Grey with metal contamination...even I ask dealer to check.. they said it is normal and keep use it.. but I think it is some bad inside... and the engine had been reassemble in February...
is it any problem in the reassemble without alignment.. anyone has experience of it... thank you