Lovelace dashboard controls disabled if control yaml template included with !include_dir_merge_list

I have a Lovelace dashboard in which some of the controls are included in configuration.yaml using !include_dir_merge_list, for example:

input_number: !include_dir_merge_list input_numbers/

The directory input_numbers is a subdirectory of config/ and the template file is minotairInputNumbers.yaml.

If I do that, the Lovelace dashboard controls are greyed out. But if I include the file directly in config/, the controls are active.

The control for the switch: key is also located in a subdirectory and defined that and it is active, as are the sensor: displays.

Why should Lovelace have a problem with certain controls but not others?

Any suggestions?