Problem with Bidirectional Relationships

I have loaded two excel (fact) tables into Power BI. Both have the same date formatting. However, when I create relationships between these two tables and my date (dimension table), Power BI imposes a bidirectional relationship on one of the tables, and a single, one-to-many on the other. I want both relationhips to be one-to-many. When I try to edit the bidirectional relationship, power BI says it is a many-to-many relationship. I have reviewed both excel tables and the date fields are formated exactly the same way, with no errors. What am I doing wrong??