"problems were found with the partition map which might prevent booting"

I have a My Passport external drive for my MAC. I have had it since March. A few days ago my drive started behaving abnormally. Sometimes showing up on my MAC, other times not. Sometimes it won’t let me eject it. Now Time Machine on my MAC fails to back up to the drive anymore. I get a failure message. The drive is connected. The light on the drive is to indicate it is running. I ran the MAC disk utility to check the drive and I get the message that “problems were found with the partition map which might prevent booting.” I have no idea how to fix this issue. Is this some kind of known issue I can resolve on my own? Or do I need to have the drive replaced (it is under warranty)?

Try to repair the partition in Disk Utility (After running First Aid to check the hard drive’s integrity). If this does not work then completely formatting and erasing your hard drive should address this issue.

Hi. Thanks for your response and assistance. As my original post
explained, when I run first aid I get the following message “problems were
found with the partition map which might prevent booting.” I also do NOT
have an option to repair my drive. My Disk Utility on my MAC (this is a
brand new MAC) only has the following options: First Aid, Partition,
Erase, Mount, Info. In fact, my interface looks completely different than
the one in the link you shared with me. And this latest time I ran Disk
Utility I got the message: “Updating boot support partitions for the
volume as required. Unable to unmount volume for repair. Operation
failed.” So, not sure what to do from here.

Im having the same problem Problems were found with the partition map which might prevent booting. I have a 3TB My Book for Mac. Now it only recognizes a 134.2MB partition and the rest appears as unallocated.

Mine is an external that is the Time Machine backup. Same message. And according to Disk utility, the 1Tb external is full. TM is supposed to delete old backups. There is only about 336GB for the entire HD it is backing up. Is there a way to delete old backups? Or, do I need to hold my breath and just reformat? It backed up about 15 hrs ago. And now, no go. There may have been a power glitch.

PS Running El Capitan on an old Macbook pro and the HD does show up in Disk Utility, but the volume is greyed out.