My external hard drive (seagate barracuda with good SMART status insidev erbatim 4TB store 'n' go) has 3 main partitions:
2) hfs+ for time machine backup
3) exfat to transfer files between windows and mac
Windows shows correctly all partitions without errors or warnings. Mac shows only 1 and 2. The third is occupied by fsck_exfat which started automatically every time I plug the hard drive in. So I force close that process, go to terminal, digit "sudo fasck_exfat -d disk1s2" and press enter. After a while it shows:
0 clusters were marked used, but not referenced
0 clusters were marked used and CLUST_BAD
0 clusters were marked free, but referenced
** Rechecking main boot region.
** Rechecking alternate boot region.
Mark volume clean?
Type yes but then:
fsck_exfat: Could not update main boot region: Bad file descriptor.
After that the disk is now visible in finder in ready only mode. I have already formatted 2 times this partition but the result is the same.