The Power Macintosh 7200 and 7500 series computers have a "kickstand" or bracket which prevents the internal component cage from opening. However, if this bracket is not secure, it can cause enough tension on the internal SCSI ribbon cable to pull it from the SCSI connector. This is the likely cause of the difficulties you are experiencing with CD-ROM discs.
To resolve this, snap the bracket securely into place and then reconnect the internal SCSI ribbon cable.
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