There are some filename validation bugs in Firefox 127+:
https://bugzilla.mozilla.org/show_bug.cgi?id=1898498
https://bugzilla.mozilla.org/show_bug.cgi?id=1903780

Currently, you can replace those invalid characters in the filename to get rid of them. For example, changing your filename pattern to:

Image Picka/${pageTitle.replace(/%|\./g,'_')}/${index} - ${name.replace(/%/g,'_')}${ext}