I don't know what is going on, so lets try a couple things. Remove two disks and connect it. See if it is OK. then connect the other two and see if the computer is OK. Are any of the drives showing "reallocated sectors" or "predicted to fail?

Lets figure out what the problem is before going further. If it is a failing disk, that can bring down the computer as you describe, so it is possible it is that.

Now, every time I have the Thunderbay connected to the computer

So I've backed up all the data to other drives but SoftRAID is unable to wipe the RAID or individual drives, erase the drives, re-initialize the drives or even to unmount the drives.   And while so doing, the entire computer goes unresponsive, each other app hangs & needs to be force quit & the computer crashes.

I've got to get this RAID rebuilt & all its data off the other maxed-out drives used for the data.  How can I get this done?