I am sorry to hear you’re having trouble. The cron node uses the cron package which should support both the five and the six value patterns.
So I’ve created the below workflow to test the behaviour you have reported:
My workflow is using the Europe/Berlin time zone, so the first execution should be at 16:00 my time, matching your pattern */5 16-23 * * 1-5.
So far it didn’t look like my workflow runs every 5 minutes but I’ll keep an eye on that over the next days. Is there any chance this might have just been a time zone problem? Which time zone do you currently have configured for your workflow? You can check this in the workflow settings like so: