Motherson Sumi can’t be clubbed with the likes of great companies for eg Gruh, HDFC, Bosch, Wabco. Nestle, P&G. Its no where near a great company. Its a good company though and featuring in Motilal Oswal does not account for anything otherwise its very easy to buy their MOST fund and do nothing.
Trust me any company whose business model is largely dependent upon a single product (exceptions where there is practically no competition or some kind of technology leadership / patent) or a large single client sometime or the other will face the brunt. The best money is made when you buy at moderate PE with an excellent growth outlook and there is complete perception change. I am pretty much sure people will make huge money by buying Page, Bosch, Eicher at current valuations. There is more downside risk then upside. When you buy a stock all one has to take care of is to know / restrict downside risk. The upside will take care of itself.