Copy Resource Plan" UI Action does not copy over some of the fields on new Resource Plan.

Most probable cause for field values not being copied over is that these are custom fields.

Copy Resource Plan UI action calls ResourcePlan Script Include's clone Method to copy over the current Resource Plan into a new one.

var fieldsToCopy has the fields to copy over in the method.

ResourcePlan : Line 970-981

clone: function(newPlanState) {
var gr = new GlideRecordSecure('resource_plan');
var fieldsToCopy = ['resource_type', 'user_resource', 'group_resource', 'start_date', 'end_date', 'request_type', 'man_days', 'percent_capacity', 'fte', 'role', 'skills', 'planned_hours', 'task', 'members_preference', 'members_list', 'distribution', 'distribution_type', 'top_task', 'program', 'portfolio', 'plan_type', 'operational_work_type', 'sys_domain'];
for (var i = 0; i < fieldsToCopy.length; ++i) {
var fieldToCopy = fieldsToCopy[i];
if (this.gr.isValidField(fieldToCopy))
gr.setValue(fieldToCopy, this.gr.getValue(fieldToCopy));
}
gr.setValue('state', newPlanState);
var sysId = gr.insert();
return sysId;
},