Hi Ironikus,
thanks for reaching out. We now are using: a strong method that replaces all emails with a “*protection text*”. That works. If we choose: automatically the best method (including javascript) the behaviour I mentioned is shown. Apparently, it’s the javascript that interferes with something else…
I tried to find out which other plugin interferes by deactivating them one at a time. But no success. Other plugins are Contact Form 7 (with Honeypot), Contact Form CFDB7, Disable XML-RPC-API, Easy Fancybox, Flamingo, Geavanceerde samenvatting, Gutenberg PDF Viewer, Linit Login Attempts. Shortcode preview, TNG WordPress Integration, Updraftplus, VS Event List, Wordfence Security, WP Header Images, Yoast SEO.
Yes, that helped. Thanks!