Slaved 2.5 HD Sata keeps malfunctioning

In other words it hangs the whole system or explorer when you try to access it. Right?
If yes, then as suggested first check the drive with its vendor made test tools. WD and Seagate have the test tools called WDDiag and Seatools.

Most of those tools won't work if the disk is connected to the PC via USB. So you will have to connect it to the PC directly to one of it's internal SATA ports.

Its a Samsung, I will look!  I really do not want to connect it to my new Optiplex....

You should check the specs on the USB enclosure.  Odds are that this old drive is SATA-1, meaning 1.5Gbits,  unless the USB->SATA bridge is ancient, it probably won't support drives that slow.

If the enclosure DOES support SATA-1, verify that you don't have to set a switch inside of it too.

If it still doesn't work, attach a different drive to make sure the SATA enclosure is good.  If that fails, get prepare to spend $500+ to a data recovery firm to get the data.   Otherwise dispose of it responsibly.

The enclosure is less than 1 year old!  

I have used with a newer Seagate SATA and it works fine!  

The specs on docking station says - SATA Compatible:  SATA-I, II, & III.

I will look on Samsung to see if it has drive utility.  I am not excited about attaching this drive to my Optiplex via SATA connectors.  I finally have an awesome machine and really do not want to open it up and start messing with connectors.  I understand all, I was a tech in my previous career, just a bit gunshy, I guess.

Samsung does not have its own utility. Use Hitachi Drive Fitness Test tool. Just google it.

The Samsung disks belong to Seagate now, use the Seagate test tool. You can also boot the PC using the UBCD, it contains most of the tools, including Samsung. But the tools on the UBCD only work with internal disks.

http://mirror.sysadminguide.net/ubcd/ubcd535.iso

Odds are profoundly high that any HDD diagnostic will work on a disk in a USB->SATA enclosure.  Reason is that this requires SCSI->ATA command set translation/encapsulation, and vast majority of bridge chips don't support the necessary instructions.

Those that do, have to use vendor/product specific commands to get it to work.  
You're just going to have to crack open the case.  Or if you have a laptop with an expansion slot for a SATA card, do that, or use another PC.

Or just give up.  As you said enclosure supports SATA-1, and it is operational.  The only diagnostic test you ran failed.  The HDD is no good.

One more gotcha .. SOME docking stations have embedded RAID controllers.  Make sure your station is dumb.   An enclosure that supports more than 1 disk and costs > $50 is a red flag.

My experience indicates that it is a waste of time if you want to fix the HDD via connecting it to your SATA / USB docking station when you are operating within Windows 7.

Try to ask for help from your friend for a spare desktop computer with SATA and connect your old HDD internally and start the computer with UBCD.

I have an older desktop that I will connect to, Windows 8.1 Pro, we will see!

the above is the best way imo: connect directly to sata cable; not only will you  have a higher speed, but also no sata to usb interface and protocol
when the drive returns ok from the test, i also run hddregenerator on it, to Ensure it' s ok

http://www.dposoft.net/hdd.html      

here is how i handle disk problems :
https://www.experts-exchange.com/Storage/Hard_Drives/A_3000-The-bad-hard-disk-problem.html

Thank you Nobus!  I need another Sata Cable, I will pick up today for my old machine!

Why do you need another SATA cable? Just use the one of the current disk in that old PC. You will be booting off the CD so the other disk doesn't need to be there.

i agrree he needs another cable, then he can use this disk as 2nd drive, backup, and more