I’ve recently upgraded to the Nik Collection 5, and I noticed a bug in the Brillance/Warnth filter.
When using that filter increasing the Warmth slider doesn’t have any impact on the image, until I put a amount greater or equal than 12%, then the actual effect “kicks” in.
I usually add between 5-10% of warmth in my shots, and I had no issues doing so using the Nik Collection 4. I can achieve a lower amount of warmth by lowering the Opacity slider of the filter, but this is really unconvenient, especially if I want to use other slider in the same filter.
I use the Nik Collection 5.2.1 on Windows 10 (64bit), with the Photoshop plugin.