Hi Philipp,
many thanks for testing and your support. I think, you’re right that another plugin may have an effect on your plugin.
I installed your plugin on three of my other sites and there, the problem does not appear and all works fine. However I can not tell you which other plugin may have caused the error in the past, as this appeared on a site for a customer and the project is finished, so that I have no access to their site.
In any case, if I will see the problem again, I will post it here.
Regards 🙂
