@murb I am experiencing this same issue. I will post some code from my solution.
`export interface IPolicyWebPartProps {
siteName:string;
siteCollection: WebPartContext;
description: string;
lists: string;
fields: any[];
context: WebPartContext;
listName: string ;
isConfigured:boolean;
isChecked:boolean;
titleText:string;
themeVariant: IReadonlyTheme | undefined;
dateSigned: any;
checkboxLabel:string;
CheckboxPlaceholder:string;
hasLicence:boolean;
baseContext: IPropertyFieldPeoplePickerProps;
}`
protected getPropertyPaneConfiguration(): IPropertyPaneConfiguration {
return {
showLoadingIndicator:this.loadingIndicator,
loadingIndicatorDelayTime: 1,
pages: [
{
header: {
description: strings.PropertyPaneDescription,
},
groups: [
{
groupFields: [
PropertyPaneTextField("titleText", {
label: strings.Title,
placeholder: strings.TitlePlaceholder
}),
PropertyPaneTextField("description", {
label: strings.DescriptionFieldLabel,
multiline:true,
placeholder:strings.Description
}),
PropertyPaneTextField("checkboxLabel", {
label: strings.CheckboxLabel,
placeholder: strings.CheckboxPlaceholder
}),
PropertyPaneDropdown("siteCollection", {
label: strings.SiteCollection,
options: this.siteCollections,
selectedKey: this.properties.siteName,
disabled: this.loadingIndicator
}),
PropertyPaneDropdown("listName",{
label: strings.ListFieldLabel,
options: this.properties.fields,
disabled: this.isFetched || this.loadingIndicator,
selectedKey: this.properties.listName,
}),
PropertyFieldPeoplePicker('people',{
label: 'Add people or group to list',
initialData: this.properties.people,
allowDuplicate: false,
principalType: [PrincipalType.Users],
onPropertyChange: this.onPropertyPaneFieldChanged,
context: this.context,
properties: this.properties,
onGetErrorMessage: null,
deferredValidationTime: 0,
key: 'peopleFieldId'
}),
PropertyPaneButton("button",{
onClick:null,
text:"Save",
buttonType: PropertyPaneButtonType.Primary
})
],
}
],
}
],
};
}