Hello Flavien,
After a long worrying time for our project we came to a very simple solution, proposed by AKnauerMaxon. Before importing or reimporting I just rename my Maxon Cinema 4D R25B folder as whatever I want and then proceed, without Cineware of course, only Datasmith.
It works perfectly, import and reimport, with all the overrides, as it always did before 5.0.3.
So we highly recommend you to not discard Datasmith and keep it as it is. We won’t use Cineware anymore, even updated, as our project would be heavily compromised in the middle of its devlopment.
We really hope you’ll take this into consideration for any future update.