Upgrade error - Upgrade from 12 to 13.00 failed at step 4

Nextcloud version (eg, 12.0.2): 12.0.3
Operating system and version (eg, Ubuntu 17.04): Ubuntu 14.04
PHP version (eg, 7.1): 7.

The issue you are facing:

Upgrade using the updater failed from version 12.0.3 to version 13. Fails at step 4 with the following message:

Create backup
Parsing response failed.

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:

  1. Open the NC updater
  2. Run the update using the update button
  3. Fails at step 4 - Create backup. Parsing response failed.

The output of your Nextcloud log in Admin > Logging:

Create backup
Parsing response failed.

Screenshot:

I will attempt to run the repair command suggested here: Upgrade to 12.01 failed, stuck in step 4

Suggested by @inX

Have you tried this command?

php occ maintenance:repair

If any advice can be provided let me know. I would prefer to use the updated than trying to manually upgrade to NC 13. Right now I am getting a 503 after this upgrade attempt so a recovery is what I am currently working on!

Regards,
Col