Disclaimer: Always maintain proper backups. 3-2-1 backup strategy eliminates the need for JBOD repair tools. Use these tools only when backups do not exist.
While TestDisk is famous for partition recovery, it is dangerous on JBODs. However, it has a niche use: If only the first few sectors of the JBOD volume (the superblock) are corrupt, but the rest of the disks are fine, TestDisk can generate a new boot sector pointing to the correct start of the MFT. Caution: Only use this on the assembled virtual JBOD, not the individual disks. jbod repair tools