Name changes of activities did not completely save.

At I have all my activities and they are almost all called "Bilzen Wegwielrennen" as I do road cycling and I am from Bilzen. Standard name given by Garmin. So far so good.

I wanted to change the names of the activities and started to do so. It went well for a few and so I continued doing so for all my 2019 activities. 

The day after, everything was still as I wanted it to be, today when I checked, most of my 2019 activities have the name "Bilzen Wegwielrennen" again! 

I guess Garmin put the old names back when I synchronized again? From my Edge 1030? From the Connect App on my mobile phone?

How to avoid this? How to keep the unique names I give to the activities? Where 's the best place to save the new given name?