If the inside assembly is loose or can wiggle, then the incorrect screws or bolts were used to mount the assembly. The correct mounting bolts should be flat and not come to a point. They are often in a separate package from the rest of the screw pack.
The package is labeled B489-109. Other smaller screws that come with the lock are for the latch assembly and the strike plate. Those screws are also wood screws, which are not intended for the inside lock assembly.
Make sure when installing the lock, you're using the correct screws and bolts.
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