@Nate I’m having a similar issue to this post: HERE. Using NLP while in the Library module, changes are not shown on the image until another slider or button is clicked, including the A/B checkbox. Both with ColorProccess: Refined & classic selected. So changes are always one step behind.
It appears to work correctly while in the develop module sometimes, also the A/B checkbox starts to show the same behaviour after a few clicks.
NLP 3.1.1 // Lightroom Classic 15.0 // OS X Sequoia 15.7 // MBP 15” x86
Adjusting converted images with the sliders on NLP’s second tab is best done in Develop view according to what @nate writes in a few of his posts. Library view works differently in rendering the thumbnails or previews and this difference might be the source of your issue. Not one of NLP, but a consequence of how LrC works.
I usually convert images in Library view. For edits with NLP, I use Develop view as recommended. Your best bet is to do the same.
I hear you, but would have thought if the changes are consistently 1 step behind, it shouldn’t be too hard to implement a refresh into the code after each change. As also mentioned, it happens to me with the A/B button and occasionally other sliders too in the develop module, it does make it difficult and slows down editing if you’re always giving a slider a second click to see if changes are displayed.