This is what the plugin Query monitor installed says after "update failed":
PHP errors (1):
wp_check_site_meta_support_prefilter was called incorrectly. The wp_blogmeta table is not installed. Please run the network database upgrade. Please see Debugging in WordPress for more information. (This message was added in version 5.1.0.)
Database error (1):
Query:
SELECT blog_id, meta_key, meta_value
FROM wp_blogmeta
WHERE blog_id IN (1)
ORDER BY meta_id ASC
This is what the plugin Query monitor installed says after "update failed":
PHP errors (1): wp_check_site_meta_support_prefilter was called incorrectly. The wp_blogmeta table is not installed. Please run the network database upgrade. Please see Debugging in WordPress for more information. (This message was added in version 5.1.0.)
Database error (1): Query:
Caller: update_meta_cache()
Error message: Table 'globalrec_db.wp_blogmeta' doesn't exist
I has happened once before. After a while it allowed to save the post.