Full-text Catalog Corruption
Looking at your errors, especially 8996, looks like a hardware problem.

Run hardware diagnostics and correct any problems. Also examine the Microsoft Windows system and application logs and the SQL Server error log to see whether the error occurred as the result of hardware failure. Fix any hardware-related problems that are contained in the logs.

CHECKDB wont be able to repair this error. Best is to restore from a GOOD backup.

Refer here for more details.