Course problems with Fenix 5+

Hello

I create a new course with Garmin Connect and transfert to my watch. When I start a new training (MTB for example) and load my course, this one is delete and the watch load the first in my list of courses (alphabetic prder).
I tried to create a course with other system and transfert to Connect with gpx format, I tried after a training to convert it to course. But in all way it's always the same

What I can do to correct or do otherwise for my problem ??

My watch is updated to the last software 18.0 and also last version of maps.