Copying all resource fields in Modx Revo admin, how?

Question

MODX

Hi all.
In the admin panel there is the ability to copy resources using the "copy" button. I use "url freezing" in my resources, that is, a fixed url is specified, when copying resources, data on freezing the url is not copied.
How to fix it?
There was an idea to write a plugin and tie it to the "OnBeforeDocFormSave" event - such as when saving, fill in the missing data on the resource, but then I don't understand how to get the data from the source (from which I copy the resource). Maybe someone will tell? Or am I not doing it right?