Thank you for contacting Garmin Europe.
It seems that all the relevant mapping data for the route that you are
trying to follow is in the Garmin, so it is likely that this message is
simply appearing because the route that you are trying to follow has
more instructions involved than the Zumo can hold within its memory at
any one time. When the Zumo calculates a route, it will attempt to
define all the instructions that you will need over the course of that
route. As the Zumo can only hold a certain number of instructions at
any one time, for especially long routes you may find in some
circumstances that messages like this can appear.
There are two things that I would recommend trying that may help your
Garmin Zumo in general.
The first is to install (or re-install) the latest software on your
device. The easiest way to do this is by making use of the WebUpdater
application. WebUpdater is a free application that can be downloaded
and installed on the computer. It guides you through the process of
updating the unit software in a Garmin device. WebUpdater can be run at
any time to check and install applicable Unit Software updates in a
Garmin device.