Hi Gary,
I am also fan of "the Simon & Garfunkel" music .
The last Helix3 update we made huge changes to prepare template for Joomla 4, also we upgraded Bootstrap.
I think the best way would be to contact with Unite slider developer and ask him about problems. Maybe it used old methods like mootools to slide images etc. On the current website I see only problem with slider, menu still works.
You can always install older version of template and keep it by now.
It's like with the music, sometimes it's worth to keep old record.
On other websites, make test with Helix3 2.0.1 version, this is the last one.