When the /core/ folder has been moved below the web root, e.g.
/htdocs/assets/
/core/components/
Then a duplicate /htdocs/core/components/mxmanager/elements/plugins/plugin.mxmanager.php file is created, as well as the correct /core/components/mxmanager/elements/plugins/plugin.mxmanager.php file below the web root.
When the /core/ folder has been moved below the web root, e.g.
Then a duplicate
/htdocs/core/components/mxmanager/elements/plugins/plugin.mxmanager.php
file is created, as well as the correct/core/components/mxmanager/elements/plugins/plugin.mxmanager.php
file below the web root.