Maplex labels with arithmetic rotation field values around 90 degrees are not rendered consistently at various scales in ArcGIS 10.3 for Desktop and later versions.
Last Published: November 9, 2015ArcGIS for Desktop
Bug ID Number
September 10, 2015
November 24, 2020
ArcGIS for Desktop
Will Not Be Addressed
The development team has considered the issue or request and concluded it will not be addressed. The issue's Additional Information section may contain further explanation.
The bug report was made on behavior that took advantage of a bug/loophole in label settings that was fixed at 10.3, but caused problems for label settings using a non-recommended combination of options.
Uncheck the Never remove option to stop Maplex labels from displaying horizontally.