Nonce is invalid" error
As I understand it, if WPDiscuz goes into the nonce validation direction, then we will all have a major issue, as nonce cannot be cached at all and we would need to remove all cache layers from all pages using the comment plugin, which means roughly the whole website.
I've rollled back to 7.3.3 also and all is working again. I won't update until this is fixed.
I have rolled back and my site is no longer crashing. That said, when we click on comments, the site slows--I love lots about this plugin but it's a bummer that it's getting worst rather than better.