Do you mean you can hear it sliding around in the tape player assembly, or you can hear it sliding around in the case? I would suggest unplugging it and removing the rear panel to take a look inside. The link below explains how to open it, although it is intended to help replace speakers. Removing the rear panel will allow access to most of the components. Once you get inside, you can take pictures and post them if you need more assistance. The second link shows how to post photos.
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