with version 5.8.7. of custom fields pro this problem still exists. I host more than 2k sites in one multisite environment. Loading the network admin needs round about 45 seconds on every page. With removing the code part explained above the pages load in 2 seconds.
In version 5.8.7. you will find the code in advanced-custom-fields-pro\includes\admin\admin-upgrade.php line 70-97.
Is there an option to fix this bug with the next release?
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