Consider the following external application.properties:

spring.profiles.active=dev
my.property=external

and the following src/main/resources/application-dev.properties:

my.property=internal

When running the application, my.property will resolve to internal, whereas documentation clearly states that it should not be so:

Spring Boot uses a very particular PropertySource order that is designed to allow sensible overriding of values, properties are considered in the the following order:
...
6. Application properties outside of your packaged jar (application.properties including YAML and profile variants).
7. Application properties packaged inside your jar (application.properties including YAML and profile variants).