Yes, I use the Nintendo save data cloud backup.
Unfortunately, it was set to automatically back up save data so I was unable to roll back to a previous save.
Achievements used to work normally for like the first 20 hours, I was looking at the list from time to time to check my progression.
A few days ago, I was playing a game (on the map Crossing in casual mode) when the Caravan achievement icon appeared. I thought it was weird since I was sure I already got it. So I checked the list and noticed all the achievements I got in the previous games were gone.
I can't remember doing anything out of the ordinary that could have triggered the bug.
From time to time, it happened that I started a game and then changed my mind (often about the vehicles to use) so I started a new game either by going back to title screen using the menu and starting a new game immediately or, in the event I did not want to play immediately, by choosing not to continue the current game when given the choice after booting the game and rather going to the title screen.
I don't know if any of this informations are useful to you. Anyway thanks for your support.