Make sure that the gearbox and motor are lined up. In addition, ensure that the bit is correctly placed and centered in the chuck after tightening it.
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The drill wobbling while in use may be caused by several factors. Make sure that the gearbox and motor are lined up by following the [https://www.ifixit.com/Guide/Ryobi+P202+Motor+Replacement/40618|Ryobi P202 Motor Replacement Guide]. In addition, ensure that the bit is correctly placed and centered in the chuck after tightening it. This could also be evident of a bent chuck and may require replacement.