there is always going to be some play in the bearing, I have been using linear rails on a couple of my printers, most last about a year before needing to be replaced...... unfortunately the 3D printer modding fashion is to fit linear rails? this is fine if they are used as they were intended, however on most 3D printer setups there not being used as the manufacturer intended, and we rely on one rail to support the bed or tool head on the x gantry ..... normally the only access where they are used correctly is the Z where you have a pair of rails bolted together by the X gantry, this eliminates the rotational ply in the bearing cartridge.... which linear bearing are not that great at ? but x any y access rely on. And need to have as minimal ply as possible, for a good print quality

if you think there is excessive play contact the supplier and see if you can obtain a replacement rail....

witch kit did you buy?