For me, it was forgetting the password on the external hard drive. After that, iCloud got to a point where I felt like backing up became unnecessary so I stoppe

For me, it was forgetting the password on the external hard drive. After that, iCloud got to a point where I felt like backing up became unnecessary so I stopped TM. (I know this isn't the response you were looking for. I've also experienced corrupt TM unrelated to HD encryption, not sure why)