On the Feature Class Properties dialog of a turn feature class in ArcCatalog, increasing the maximum number of edges per turn on a turn feature class causes the following error:
Unable to alter maximum number of edges per turn.
General function failure
Too many fields defined.
Increasing the maximum number of edges on a turn feature class by one causes the addition of three fields. If there are too many fields already present on the feature class, then the error occurs when attempting to add these new fields.
The maximum number of allowed fields on a table varies by DBMS. For example, a personal geodatabase can only have a maximum of 255 fields.