it looks likely that you didn't setup the u-boot env variables correctly.
setenv bootcmd 'mmc read 0x40000000 0x00004400 0x0010000; fdt addr $(fdtcontroladdr); fdt rm /signature; bootm 0x40000000'
setenv dual_boot.slot_0_invalid 1
setenv dual_boot.slot_1_invalid 1
setenv bootmenu_default 7
saveenv
Is what's currently working on my Vero (near identical hardware).
Note that that first line is long.
You can check via 'print' from u-boot.
(the 7 is one higher then any existing boot menu option - might need to be 9)