Field Skipped When Multiple SharePoint Tasks Requested

I have encountered some unexpected behavior when using Microsoft Graph to request data from SharePoint task lists. I discovered this using MS Graph in C# and I have reproduced it in https://developer.microsoft.com/en-us/graph/graph-explorer

Here is an example of a query for one specific task (Id: 61) requesting fields: 'Title', 'Milestone', and 'Area' ('Milestone' and 'Area' are custom managed metadata fields). In this case, all columns are returned properly.

The next query is identical except, instead of requesting only one task, I am requesting all of the tasks in the list. This time the 'Milestone' field is not included in the result for item 61.

This happens with every task in the list. If I request an individual task by id I can retrieve all fields correctly but if I request multiple tasks I cannot retrieve the 'Milestone' field.  What could be causing this behavior?

Thank you!