https://jp.ifixit.com/Answers/View/810294/On+off+switch+not+holding,
On off switch not holding, - Meuleuse d'angle filaire Dexter 2100W - 2100AG2-230.5 - iFixit
Put into on position but switches on and off whilst operating - Meuleuse d'angle filaire Dexter 2100W - 2100AG2-230.5