PlatformUI is not compatible with REST basic auth. This makes it look like a bug, for ex EZP-27184
Until EZP-22192 is implemented, we should add a waring message on top of the configuration block.
EZP-27184 Unable to login after enabling basic http auth for rest
EZP-22192 Allow both basic and session auth at the same time
EZP-27760 Add information about not allowing both basic and session auth at the same time
PR on 1.7