There is an entirely different method to Open files with the dreaded .cwk file suffix, but it requires the use of the Devil's Seed, MS Word...
In the Finder, click on the filename to highlight it. Now deselect and select just the suffix ie .cwk
Change “.cwk” to “.doc” (Don’t forget the dot.)
Deselect it, (you will get a dialogue asking if you want to change the extension from .cwk to .doc. Click “Use .doc”
You will now get another dialogue box headed “Convert File”.
Scroll to the very bottom, and there is an option “Recover Text from Any File.” Select that, and click “OK”.
You will get another dialogue box, saying “this file needs to be opened by the Recover Text from Any File …… etc…”
Click OK.
It will Open in Word. Remove all the extraneous crap before and after the actual copy, and Save As a new version, .docx I believe.
Works for me, including with 150 page documents.