UUIDs are not hardware-specific but stored in the partition's filesystem. That means cloning a disk or partition with dd will result in the same UUID. However recreating the partitions manually on the new disk (e.g. smaller disk), will result in new UUID. This could result in problems when booting the new disk uses UUID in fstab.

cat /etc/fstab
# /etc/fstab: static file system information.
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sda3 during installation
UUID=b2fa29ee-670f-4d44-becc-d9ec368d4a41 /               ext4    noatime,nodiratime,errors=remount-ro 0       1

This can be solved by either changing the entries in fstab to the old style: /dev/dbX, Or by getting the new UUID and update fstab accordingy:

# blkid /dev/sdb1
/dev/sdb1: UUID="34628ffd-58e6-4a58-9b4d-533719305931" TYPE="ext4" PARTUUID="fa64ccff-01"