say: install everything that belongs to that kernel(irrc that are three packages). put a copy of the kernel to your pc(so you have it in case something goes wrong). also deinstall uboot. and if uboot is still there after that use force and flash the kernel you saved on your harddrive(must be the one you prev. installed via apt). and you are good. (note that i said flash KERNEL not firmware and not emmc. that is: flasher -f -k kernel) also note the order first use the most high level means of doing it and only if they are buggy and fail use brute force to achieve where that failed.