Hi Willianxz, thank you for looking at this in such detail. The plugins are up-to date, I use contact-form 5.1.1, and it happens only on mobile phones. If I resize my brwoser window to get it to swtich to the mobile version, than it works for me as well.
I have tried now with a different browser on the phone, the newest Chrome and there it always jumps to the bottom of the page. Before that I tried it the Samsung Internet Browser, where it always jumps up.
Regarding the duplication, it seems the mobile form as well as the dektop form if you are in the screen-size you mentioned, thanks for pointing it out, that’s something that I can fix.
I have a guy who build the site originally, guess I’ll ask him to figure out the form problem, I have deactivated and activated the plugin, changed field names, and created a new form, but did not help. So, thanks for your effort, it is very much appreciated.