Greetings,
it’s hard to know without access to the WordPress back-end. Most likely there’s some kind of script/plugin/module/configuration triggering this. As a simple test, you should go to:
Advanced > Templates > Flag template
Locate and remove:
href="javascript:;"
So it then looks like this:
...a onclick="PrisnaGWT...
If this doesn’t work, and your hosting provider also cannot assist you, then please send a WordPress admin access and we’ll take a look:
https://www.prisna.net/contact-us/
Regards