Adjusting saddle angle impossible due to stuck part

I‘ve finished assembling my new Bike Plus and wanted to adjust the saddle angle. The screw came off without any problems but I realized that one of the cone shaped parts does not. With that, there is no way to adjust the angle of the saddle.

Have you had something Imitat on your bikes or is there an easy fix to it? I‘ve tried removing the part with a rubber hammer but it won’t move a bit. Maybe some grease?

Thanks for any feedback!

Cheers

Sandro