Validation error and warning for PML Object

I am getting a validation error for the substrate I am using:
"Object 'substrate' does not use the PML naming convention, but is a PML object. This may cause incorrect fields to be calculated. It's name must begin with PML".

Is there a way I can "un-assign" it as a PML object ?

Another HFSS validation warning I notice: "PML group 'PMLGroup3' part 'substrate' is contained by object 'ABC' ".
My history tab does not list any PML group trees.

I therefore also want to locate this 'PMLGroup3' list so that I can modify the PML assignments, if possible.

Kindly suggest how I can rectify this error or warning.

Thanks,