Here is the reply which I got for my complaint regarding the shaking of coach S13 in 12657:
Train No 12658/57 SBC-MAS-SBC Chennai Mail Express is integrated with 1267/28 SBC-NDLS-SBC Karnataka Express is primarily maintained at SBC. S13 coach No WGSCN-07257 and all the coaches in the train have been thoroughly checked in all respects like under gear examination, cleaning,watering , safety amenity fittings , seats, berths etc and departed from SBC on 15.03.2017. Based on the complaint of train the bogies, wheels and running gear of coach No S13 (WGSCN-07257) have been examined thoroughly by the maintenance team. The coach was also kept under observation while on run by the team supervisor to check for any undue vibration/sound, and cleared for...
more... normal use after being satisfied that there has no abnormality in the said coach. We regret for the inconvenience caused.