RPI-Clone an SSD to an SSD - Fails with I/O Error

I have a RPi 4 system with 4GB RAM and another 4GB with ZRAM.

It is running XFCE and I’ve successfully converted from SD to SSD. Everything works fine here as of right now.

Recently I’ve attempted to Clone the Boot/Root SSD to another SSD, but it doesn’t seem like the Raspberry Pi can handle this very well.

I am doing the clone by using rpi-clone and executing rpi-clone sda -v -f -L SSD-RPi as root.

The rsync copy works fine up to a certain point, where the transfer just fails due to an input/output error.

rsync: recv_generator: mkdir "/mnt/clone/var" failed: Input/output error (5)
*** Skipping any contents from this failed directory ***
var/

sent 429,998,130 bytes  received 319,856 bytes  2,006,144.46 bytes/sec
total size is 4,348,546,020  speedup is 10.11
rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1207) [sender=3.1.3]

mkdir: cannot create directory ?/mnt/clone/boot?: Input/output error
  Mounting /dev/sda1 on /mnt/clone/boot
mount: /mnt/clone/boot: can't read superblock on /dev/sda1.
    Mount failure of /dev/sda1 on /mnt/clone/boot.
  unmounting /mnt/clone
Aborting!

The mounting of the new SSD also fails at that point.

To me it seems like the raspberry Pi USB-Bus can’t handle this clone.

But I still wonder, is this in any way possible? Can I establish a more reliable cloning-process on the Raspberry Pi?

My goal would be to clone the ssd, so I can switch over without reconfiguring the whole system.

The components I use:

• Crucial BX500 240GB CT240BX500SSD1 (= Current SSD that is being cloned from aka. root)
• Corsair Force Series MP510 240GB (= Destination SSD)
• DeLock SATA to USB Adapter (= USB-Adapter for Current SSD aka. root)
• ICY BOX IB-1816M-C31
• Original Raspberry Pi 4 Power Adapter

I suspect that the components also might not be optimal for this.

So yea..

I feel like I have to do the "Turn SD to SSD"-Process again with the new SSD again. Which would be somewhat painful, thus I wanted to figure out if there were options to do a reliable "copy" on the Raspberry Pi itself with everything connected.

UPDATE with info from a comment:
Both are powered by the PI USB ports. It’s not the most optimal setup there is.. I could try with a powered USB Hub. Also yes, I have rights to that directory. The error points that say the files are "locked" are due to the failure of the drive at that point. Meaning the files aren’t accessible anymore because of a disconnection of the drive.