after copying 1 disk to a second disk both well not boot up

hey brothers and sisters,
here is the story:
i had 2 hard drives on my laptop because i was not fully confident in my linux Skills and i felt like i needed a windows install just in case,
lately i have become a lot more confident with linux so i decided to get rid of the windows installation and move the ubuntu installation to the original disk where i use to have the windows installation,
and use the second disk for buckups and such,
and also use the second disk to perform restores from timeshift and such to practice restores and get comfortable with them and some other risky stuff,

now here is what i did:
i used a usb flash drive to boot into a live ubuntu,
i opened terminal and run:
sudo dd if=[name of disk where i had ubuntu] of=[name of disk where i used to have windows],
i waited for 45 minutes and eventually it was done,
i checked and the disks have identical partitions,

here is the problem:
when i tried booting from either of the disks it kept on getting into built-in shell,
i tried 'exit' command and it did nothing,
i tried 'fsck [partition name] -y' command on different partitions and all partitions were perfect,
eventually i just grabbed one of the disks and pulled it out,
that solved it!!,
so my guess is that the problem is the existing of two identical disks with identical partitions and identical booting info,

now i'm using the laptop with only one disk connected but i would love to be able to boot into either one of those two disks without changing to much on neither,

any help would be amazing,
love you all