Inconsistent responses from SharePoint365 API

jcgonzalezmartin 

We authenticate with Sharepoint API using SharePoint App-Only principal as documented in https://docs.microsoft.com/en-us/sharepoint/dev/solution-guidance/security-apponly as our app way to run software that integrates with both online and on premises Sharepoint installations. That was what was meant with legacy.

Apologies.

The inconsistencies we are seeing are solely related to the Sharepoint REST API documented in https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/get-to-know-the-sharepoint-rest-service

For full clarity purposes, the endpoints we are having issues with are 

GetFileByServerRelativeUrl and GetFolderByServerRelativeUrl (described in https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/working-with-folders-and-files-with-rest ) which we use to navigate Sharepoint sites.