Error generating hard link while apt upgrade running initramfs-tools

When running sudo apt upgrade yesterday on my Rock Pi 4 I get following error (Output was in german, I translated it here):

ln: The hard link ‘/boot/initrd.img-4.4.154-110-rockchip-gcef30e88a9f5.dpkg-bak’ => '/boot/initrd.img-4.4.1
54-110-rockchip-gcef30e88a9f5 'could not be created: Operation not permitted.

apt upgrade ends normal and a reboot works fine as well.
When I call uname -a now I get:

Linux linux 4.4.154-110-rockchip-gcef30e88a9f5 #1 SMP Mon Jun 22 07:37:10 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux

So I am wondering what this error is, if I have to fix something or just go on using my system since the next ubuntu updates.
Also this error seems similar to that reported here

Does anybody have an idea what to do in case of this error?



I think it should be the fat filesystem can not create link. It should not cause any real issues.