Follow Up – I got this message from our host, Flywheel:
Hey Alex,
We are sorry this issue is still ongoing. After further investigation, we’ve come to a couple of conclusions. In the logs, you will see this line:
0007.671 (0) PHP event: code E_WARNING: php_uname() has been disabled for security reasons (line 5687, wp-admin/includes/class-pclzip.php)
We disable the class php_uname() for security purposes. However, that is not the actual issue, as the class is simply being used to transpose slashes ( screenshot: https://i.getf.ly/kpuLe2GO ). We also disable this on our legacy platform as well and Updraft works there. This doesn’t seem to actually prevent backups from working.
The issue might be due to the way UpdraftPlus detects the root directory as well as our file structure. The Flywheel Cloud Platform has separated the WordPress core files away from the root directory. The WordPress core files are actually symlinked from the /.wordpress directory now.
The way we have WordPress core files segmented is something many Cloud WordPress hosts are doing now, for security reasons. Our engineers confirm this is following WordPress best practice.
WordPress has been trying to direct developers to use these constants to define where the directories are located: https://codex.www.ads-software.com/Determining_Plugin_and_Content_Directories
You may want to reach out to UpdraftPlus about this issue. Other backup plugins, like BackWPup do work on our cloud platform, but this would require an adjustment from the client. We apologize for the inconvenience.
Regards,