In a very recent change I made in MEN-3725 I added partuuid support to mender-convert for referencing block devices by bootloader/kernel/fstab/mender. This implementation used device paths in fstab which happen to be symbolic links created by udevd on boot. Further testing has revealed that this is less than stable as the way systemd works, can result in un-resolved symlinks in mount units if the device does not exist at the time systemd-fstab-generator runs.
Using the key/value notation in fstab fixes the problem as it no longer has a dependency on udevd devices being present early in boot sequence.
the proposed fix is to replace paths in fstab with key/value notation if partuuid feature is requested.