I've been dealing with this for quite some time. Looked for a solution on the forum, but did not find one.
Whenever I make a change utilizing Nik through LR, non of the data (keyword) is saved. For example, if I am working on 10 photos of Mr Smith and edit one via Nik, the edit (11th photo) will not show up when I return to LR. I have to uncheck Mr Smith from the keyword list, find the photo, add the keyword and then close and relaunch LR.