Backup and restore

Hi All, getting the below error when completing a test or opening some files on my moodle site.

An error occurred while processing your responses (Error writing to database). Click continue to return to the page you were on and try again.

Link takes to blank forum post.

Can navigate and make changes to profile (example) fine

When to run http://serverip/admin/cron.php and get the below error:

Server Time: Thu, 02 Aug 2018 19:24:05 +0100


Execute scheduled task: Site registration (core\task\registration_cron_task)
... started 19:24:05. Current memory use 3.5MB.
Your site is not yet registered.
... used 1 dbqueries
... used 0.014724016189575 seconds
Scheduled task complete: Site registration (core\task\registration_cron_task)
Execute scheduled task: Cleanup old sessions (core\task\session_cleanup_task)
... started 19:24:05. Current memory use 4MB.
... used 62 dbqueries
... used 0.15144801139832 seconds
Scheduled task complete: Cleanup old sessions (core\task\session_cleanup_task)
Execute scheduled task: Delete unconfirmed users (core\task\delete_unconfirmed_users_task)
... started 19:24:05. Current memory use 4.1MB.
... used 1 dbqueries
... used 0.00056099891662598 seconds
Scheduled task complete: Delete unconfirmed users (core\task\delete_unconfirmed_users_task)
Execute scheduled task: Delete incomplete users (core\task\delete_incomplete_users_task)
... started 19:24:05. Current memory use 4.1MB.
... used 0 dbqueries
... used 5.5074691772461E-5 seconds
Scheduled task complete: Delete incomplete users (core\task\delete_incomplete_users_task)
Execute scheduled task: Clean backup tables and logs (core\task\backup_cleanup_task)
... started 19:24:05. Current memory use 4.1MB.
... used 2 dbqueries
... used 0.031139850616455 seconds
Scheduled task complete: Clean backup tables and logs (core\task\backup_cleanup_task)
Execute scheduled task: Background processing for tags (core\task\tag_cron_task)
... started 19:24:05. Current memory use 4.1MB.
... used 6 dbqueries
... used 0.073811054229736 seconds
Scheduled task complete: Background processing for tags (core\task\tag_cron_task)
Execute scheduled task: Cleanup contexts (core\task\context_cleanup_task)
... started 19:24:05. Current memory use 4.1MB.
 Cleaned up context instances
... used 6 dbqueries
... used 0.0044808387756348 seconds
Scheduled task failed: Cleanup contexts (core\task\context_cleanup_task),Error writing to database
!!! Error writing to database !!!