During the first turn of a goods party, liberty bells will not reflect the effect, unless you move units to/from the town hall. In the attached game, on this turn I rejected a tax increase and Fort Maurtis started a goods party. At first, with two ES at the town hall I it said 19 bellls. Removing one ES increased the bells to 20, and added the goods party to the production modifier report.
Files provided in case they are useful. Can't really reproduce this, as if you get a tax increase demand and then start the same turn over from an autosave you never (in my experience, and I have to admit I've done this more than I should) get another demand on that same turn (IOW, if you set autosave to every turn, you can effectively cheat your way out of any tax increases).
I can say I've seen it several times, so I don't think this game is a fluke.
Ugh, glad you found that one. Feature change messages were completely failing. The only good thing is that FreeCol would recover correctly after being kicked (such as by moving the unit in the town hall). Should be fixed in git.0448dd8. Setting to Pending until next release.