System is on eMMC.
Thanks for this hint about verbosity, I didn't see it anywhere on wiki
So, I boot on fresh install on sd card, changed verbosity then reboot on eMMC. I found culprit, a custom mount point prevented system for booting after cleaned it up, system boots fine !
Maybe these simple diag step needs to be published to help people
Sorry for my annoyance in the previous posts, but it's true that it's starting to get boring such an unstable system (reboot every day or so).