Home assistant yellow boot issue

Hello,

I have a big issue with my two Yellow. I have a rpi module with eMMC include and a external ssd connected to m.2 socket. First system was installed on the emmc and I migrate it to the ssd after.

Now sometime when I shutdown the yellow board, the system boot on the emmc not the ssd.

Could you please help me force the cm4 to boot only on ssd ?

Best regards,

Julien