update-initramfs -u fails with random resume UUID

[UlfZibis]

Ubuntu 16.04 32-bit
In fstab I have:
UUID=38e6603c-6b17-488a-9613-7341e8e89274 none swap sw 0 0
But I have 2 swap partitions on my hard drive, the other for a 64-bit instance.
With this setting, suspend-to-disk (STD) was functional in ~ 50 % of the cases.
Then I created /etc/initramfs-tools/conf.d/resume with:
RESUME=UUID=38e6603c-6b17-488a-9613-7341e8e89274
and did sudo update-initramfs -u -k all.
After this, the STD never worked again. So I extracted /boot/initrd.img-4.4.0-78-generic and saw the surprising content, different from the swap-partitions UUID:
RESUME=UUID=93782983-700c-4084-84b1-5e3f8c1e788f
Another try of sudo update-initramfs -u -k all created another random UUID, both do not match with any partition UUID on my system.

So I recovered my original system back from a backup image and discovered in conf/conf.d/resume from /boot/initrd.img-4.4.0-78-generic:
RESUME=UUID=38e6603c-6b17-488a-9613-7341e8e89274
So originally there was the correct UUID, even I never created a /etc/initramfs-tools/conf.d/resume file.

Now I do not have any idea, why sudo update-initramfs -u -k all doesn't create correct values to make STD always working reliably.