Thanks for your useful plugin!
I just upgraded to Version 2.66.6 and it removes the previously inserted "Post Category Tags" and replaces them with a "1".
In addition, it unchecks the check-boxes for Filter Words to be excluded.
Re-inserting the tags, checking the boxes, and re-saving does not help. It reverts to the previous state.
I have thus gone back to a previous Version 2.66.3 (*see why, below), and it resolved the issue.
*P.S. In addition, I have just realized that Version 2.66.5 had also wiped the Post Tags, but not replaced them with a "1". And it similarly removed the excluded filters. I also think that this version, and maybe even the one before that, had stopped working, by not updating feeds anymore. The last version that I'm sure did in fact update RSS feeds, and not have these other issues is Version 2.66.3.