Microsoft.Teams.Graph.Svc.conversationIdentityType could not be resolved

Has anyone else seen this message: "Microsoft.Teams.Graph.Svc.conversationIdentityType could not be resolved"

I'm getting this error part way through a query that otherwise (seems) to work fine

Watching Fiddler, I can tell that no HTTP error is raised

It's a MS Graph API query

I can only circumvent this by deleting all rows of the query from the row on which the error occurs, but that leaves me with a much truncated dataset

Any ideas welcome