I am experiencing a similar issue with Titlecase formatters on SC and AC.
Using this in SC db insert and db update actions and also on AC data bindings and doesn't work in all cases.
Sorry @JonL, but your test seems not to be completely waterproof:
Okay, thought it was a similar issue, because I am on NodeJS also, trying to use server side binding titlecase formatter to convert a string in a server action within my database insert/update action step.
Will open a separate bug report then
Update for the capitalize, unzip in lib/formatters. This update will not be included in todays Wappler update since we want to verify first if it is working and will then be included in next weeks update.