Not working on mobile devices!

Hi, it seems that the plugin doesn’t work properly on mobile devices.
When clicking on the button, the first time the user gets send to the paypal homepage, not to the donation details page.
When I click on the button the second time, it works correctly.
On desktop it works perfectly.
You can see it here: https://movingroovin.de/spendenaktion-2016/ (scroll down to the end of the post)

Any advice?
Thanks!