Akeeba Backup for WordPress Internal Server Error 500 XHR ReadyState: 4

I experienced this error when trying to run a backup on a site hosted at the One.com provider.

The solution is to manually adjust the JPA part size for split archives. Even if the configuration wizard had been used, it didn’t work.

1. Go to Akeeba Backup -> Settings
2. Scroll down to Archiver engine where JPA is selected.
3. Click on the Configure button to the right of JPA.
4. In my case the Part Size for split archives was set to over 2 GB. I lowered it until it worked, which for me was 100 MB.