Filemaker: behavior of portal rows

Question

I am creating a contacts database using FileMaker Pro 19. Part of the relationship diagram is shown below:

For each Person record, I have zero or more Phone records, each corresponding to exactly one IDDCode record.

In the layout for editing Person records, I have a portal (with all default options) pointing to the Phone table. In each portal row I have edit boxes for the Phone::Label and Phone::PhoneNumber fields, and a drop-down control with "Display data from" = IDDCode::DisplayCode and the "Values from" list set up as:

Hopefully it is clear enough what I am aiming for. What actually happens is not even close to that. Among the many unexpected behaviors:

• Changing one drop-down sets the value in all rows
• The values shown in the drop-down do not necessarily correspond to the values in the Phone table
• When I open the drop-down list, the highlighted default is off by one (e.g. if IDDCodeID is 39, the value for IDDCodeID 40 is highlighted)
• Some of the edit boxes are missing, e.g. the second row in the example image should have a phone number filled in

The portal does correctly display the existing (imported) data, though. Here is an example of what I see when I try to use the layout:

QUESTION:

Obviously the way I have set this up is wrong (I am familiar with databases but brand new to Filemaker). Rather than address the problems with my setup point by point, I am hoping to find out what is the right way to do this in Filemaker?