Table usermeta doesn’t exist for query INSERT INTO `usermeta`

Thanks for getting back, there were a few occurrences but it’s not now reproducing, so I’ll close for now until I can reproduce it.

It definitely is reproducing, albeit not as often as I would expect.

the example errors are:
[16-Jun-2018 10:04:54 UTC] Error Table ‘<mysite>_www.usermeta’ doesn’t exist de la base de datos de WordPress para la consulta INSERT INTO usermeta( user_id, meta_key, meta_value )
VALUES ( ’93’, ‘_woocommerce_persistent_cart’,

I don’t understand what this user_id is: there is no user and the the user_id passed is sequentially increasing with every error in a way that has nothing to do with the actual user ids.

Tracing through your code I can see where the problem is but so far I don’t have clear what the code is trying to do or why…

in wcal_class_guest.php
This action is hooked only if the user is not logged in:

if ( ! is_user_logged_in() ) {
  add_action( 'wp_ajax_nopriv_save_data', 'save_data' );
} 

and the function then reconfirms the user is not logged in:

function save_data() {		
        if ( ! is_user_logged_in() ) {

ll 272+ there is code like:

if( is_multisite() ) {
 // get main site's table prefix
 $main_prefix = $wpdb->get_blog_prefix(1);
 $insert_persistent_cart = "INSERT INTO <code>&quot; . $wpdb->main_prefix . &quot;usermeta</code>( user_id, meta_key, meta_value )
    VALUES ( '".$user_id."', '_woocommerce_persistent_cart', '".$cart_info."' )";
  $wpdb->query( $insert_persistent_cart );

} else { 
  $insert_persistent_cart = "INSERT INTO <code>&quot; . $wpdb->prefix . &quot;usermeta</code>( user_id, meta_key, meta_value )
    VALUES ( '".$user_id."', '_woocommerce_persistent_cart', '".$cart_info."' )";
   $wpdb->query( $insert_persistent_cart );

Well, from the logs it looks like in certain circumstances $wpdb->get_blog_prefix(1) might not be getting the right value, but even without that, there is no real $user_id and it doesn’t seem make sense to be updating the persistent cart of a fake/random user id?

The $user_id is an id returned from the insert of an anoymous user into ac_abandoned_cart_history_lite

//Insert record in abandoned cart table for the guest user
$user_id			 = $wpdb->insert_id;

, it should not be used to update a record in the real wordpress usermeta table.

So I’m wondering whether I can ignore or comment out this part of the code or really what is it supposed to be doing?

Yes in this case it is multisite..
.. but the code also seems not correct for single site