Basecamp Problem Transfering Routes to Oregon 600

Hi there

couldnt find any answer to my question in the FAQs.

I am running basecamp (4.4.6) on a Macintosh (10.9.5). When having finished designing my routes on Basecamp and transfering them to my Garmin Oregon 600 I get only straight lines between the waypoints (in most cases therefore just between start and arrival). The route is designed on the same topographic map which is on the SD chip on the Oregon 600.
My workaround this problem is to transfer the route into a track and then just working with the track on my Oregon. What is the problem? Why routes are not transferred correctly?

Thx Georg