thansk John
sent you a message with file. thanks Owen
The keywords in the catalog you sent were indeed corrupted, in a way that I hadn't seen before. I sent you a Dropbox link to a corrected copy of the .lrcat file. It's surely a bug in LR that corrupted the keywords, though no one has been able to figure out a way to reproduce the bug so Adobe could fix it.
Be sure to make a backup copy of the current catalog, then replace it's .lrcat with the corrected one and delete the Helper.lrdata file (all while LR is not running, of course).
There were many keywords containing commas, e.g. "apple, crates". LR doesn't allow commas, but it doesn't always check to prevent them. The commas in your keywords probably came from photos that you imported after they were modified by programs or services that don't conform with industry metadata standards.
I don't know for a fact that the presence of these commas in your keywords caused the corrupted keywords, but there's a strong possibility they did. So in the corrected catalog I sent you, keywords containing commas, e.g. "apple, creates", were replaced with multiple keywords, e.g. "apple" and "crates".
Before doing more "real" work with the correct catalog, I recommend you poke around the keywords and tagged faces, making sure the keywords are what you expect and appear to be working correctly.