Solution has comed with an update, as stated in Work with Python and R modules | Databricks on AWS, In Databricks Runtime 13.0 and above, directories added to the Python sys.path are automatically distributed to all executors in the cluster. In Databricks Runtime 12.2 LTS and below, libraries added to the sys.path must be explicitly installed on executors.

This seems to have solved our strange import problem from Databricks Repos