The method export() does not exist on Aimeos\Admin\JQAdm\Iface. It seems like you code against a sub-type of said class. However, the method does not exist in Aimeos\Admin\JQAdm\Common\Admin\Factory\Iface or Aimeos\Admin\JQAdm\Common\Decorator\Iface. Are you sure you never get one of those?
Ignorable by Annotation
If this is a false-positive, you can also ignore this issue in your code via the ignore-call annotation