We recently noticed that several full backups of our site had failed. At that time, we were using a previous version of Akeeba Backup Pro.
We installed the latest version, and ran a full backup manually via the One-click Backup button; this completed successfully, generating a .jpa file and 15 .jnn files.
The next day, a scheduled full backup failed, while generating file .j14. At that time, the log file was not recording debug information. We turned on debug logging, and the scheduled full backup again failed the next day, while generating file .j12. The log file from this backup is attached.
After this fail, we ran a full backup manually, which completed successfully.
Scheduled incremental backups are all completing successfully.
EDIT: Original zipped log file failed to upload. Here's a link to a re-zipped version: https://drive.google.com/file/d/1oPPh1oOpLeExgmvGYaQp_ErUHZV4Kba4/view?usp=sharing