During the fitting of your tap the installer will need to remove the cartridges from their valves to cut them to the appropriate depth for your walls. On reinserting them however it is important that the cartridges are tighten to the factory setting of 4Nm identified in the installation manual. If this is not done, then it will be difficult for the handles to perfectly align horizontally (or vertically). If this is the case, and your installer does not have a torque wrench available, they should just tighten the valve by the small amount required to allow the handle to align.
If they are unsure how to do this then they are welcome to contact us where we have a dedicated support team ready to help.