I believe I forgot some important data here.
It is under Linux Mint and this external disk is used as root partition.
So with the default USB driver I had this behaviour and no access to SMART data and energy settings.
I ve then changed the driver for an old one and this last one give access to these features. I could then disable the APM in Disks (gnome-disk)
nb : gsmartcontrol seem to reset the APM to the default one
I wonder why I had not fixed this behaviour before ... I remember that for me this old driver was not very good in the data transfer rates (?)
so 3 years after it must have been improved I guess, and that's what can have fixed this.
1 178 708 head parkings later it is still alive
The 3 errors, happened before this "million"