Okay, I found out some more things. When flashing my NAND via u-boot I have two different possibilities: either I use the nand write or the nand write.trimffs function (which is also handled here: clicky, more infos: clicky). The first one will lead to a successful boot, but I cannot reboot then due to a ubi_io_read error. with lots of ECC errors. BUT: the checksum of the ubi0_1 volume matches then the one from my host build. On the other side, the second command will lead to a perfectly fine reboot, but the checksum differs (as 0xff data at the end of pages will not be written to the NAND flash). As a result (and as far as I can see) I either have to fix my reboot issue with the normal nand write OR ensure that the kernel writes in a nand write.trimffs mode …