@crayon , thank for your reply.
I do proceed to an autoleveling each time because I though it was necessary.
I don't know how to 'calibrate' the offset, it's 0.25 configurated and I didn't change it.
The firmware is not latest : 1.0.2 if I remember.
I did'nt read some good effect of upgrading the firmware, so I prefere not to do now.
I print directly from SD card, the printer is not yet connected to my computer.
The cat come from the SD card in G-code format.
The phone holder come from Thingiverse, I didn't change the parameters to slice it, maybe the density (I don't remember).
I read a lot on the net yesterday evening, first thing to verify is the cleaning of the bed.
Because I found the cat outside the bed on the display, so I guess it was not stick.
This morning I proceeded to some checks :
- tension of the belts, didn't check the screws (I will do)
- cleaning the bed (I don't have any alcohol, so I used 'window cleaner with alcohol')
- auto leveling again
I started again a new model (smal figurine) and had to stop it because it printed some parts in the void again.
I understood that I didn't put supports, so now I'm busy to print another one with supports and extra adhesion, hope it will work (35 %, it takes 3 x more time)
So, I suppose that I had two problems :
- missing supports on the other model
Maybe another idea for the non sticking : I changed the printer to another room, because the fans are too noisy, but this room is colder (19°C). Could be ?