Removed keywords still 'stick' to image, new keywords don't (LR CC)

[greggm29504944]

• Uploaded a few test JPGs to test keywording & search.
• I removed a keyword X from an image & then searched for 'X'.
• The image still appears in search results, although 'X' is no longer on keyword panel (or other field).
• Went away for a couple of hours in case it was a cache thing, signed back in: same.
• Downloaded the file & it still has keyword 'X' on it.
• If I add a new keyword Y in LR CC, it shows on the keyword panel but not on the downloaded file.
• However, edited Titles do show in downloaded files, and searching on LR CC works okay.

TL;DR Info displayed in LR CC keyword panel is different to actual image.
How do I make them the same? Your help much appreciated!

[greggm29504944]

So maybe from a different angle: What LR-CC changes are actually written to file? And which ones aren't?

Is there an Adobe resource with this info?