I've created a custom search vertical under Microsoft Search settings in a modern SharePoint Online site collection. There are couple of fields which are multi select Managed Metadata and Person or Group fields. The data is stored in them in the format which is given as follows:
Company (Managed Metadata) - ABC Inc; XYZ Pvt Ltd
Author (Person or Group) - User1;User2 (display names)
The above 2 fields are used as filters and the respective RefinableString managed properties are used with corresponding crawled properties.
Company - OWS_Company (managed metadata), OWS_Company2 (lookup), OWS_CompanyName (multiple lines of text)
Author - OWS_Author
When we try to filter the search results, the available options in the dropdown are shown in the format that is stored in the library instead of showing single values for the person or group column and it displays correct values (single values) for the managed metadata field.
XYZ PVt Ltd
XYZ PVt Ltd
The Company field's (managed metadata) managed property has 3 fields crawled properties mapped to it of type Managed Metadata, Lookup and Multiple lines of text whereas the Author (person or group) field only has one crawled property of type person or group.
Based on PnP Community support and a related reddit thread, this is a search API issue for which the fix has been rolled out few months back but we are currently still seeing this issue. Any thoughts or ideas on how to resolve this?