I made some further tests and it appears that the issue was caused by these rules in .htaccess:
<IfModule mod_headers.c>
<FilesMatch "\.(ttf|ttc|otf|eot|woff|woff2|font.css|css|js)$">
Header set Access-Control-Allow-Origin "*"
</FilesMatch>
</IfModule>
# BEGIN WordPress
# The directives (lines) between "BEGIN WordPress" and "END WordPress" are
# dynamically generated, and should only be modified via WordPress filters.
# Any changes to the directives between these markers will be overwritten.
<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType image/jpg "access plus 24 hours"
ExpiresByType image/jpeg "access plus 24 hours"
ExpiresByType image/gif "access plus 24 hours"
ExpiresByType image/png "access plus 24 hours"
ExpiresByType text/css "access plus 24 hours"
ExpiresByType application/pdf "access plus 1 week"
ExpiresByType text/javascript "access plus 24 hours"
ExpiresByType text/html "access plus 2 hours"
ExpiresByType image/x-icon "access plus 1 year"
ExpiresDefault "access plus 24 hours"
</IfModule>
Options -Indexes
<IfModule mod_headers.c>
Header set X-Endurance-Cache-Level "2"
Header set X-nginx-cache "WordPress"
</IfModule>
When they are removed the currency changes.
You may check with the developer of the plugin why they interfere with the functionality.
This is the reply from the server hosting side, please check this and let me know if this is helpful