Hello @Jordi,
The error ‘Error Calculating Route’ relates to a bug we are aware of that is caused in a failure when trying to find a route using Google Directions API. We have been looking into this issue and are deploying a fix today which we hope to alleviate the problem. After today if you are still receiving these errors please let us know.
If you put the contact phone number in the comments field then the driver will be able to see this information (as opposed to the number being anonymised in the contact phone field), therefore we do not recommend putting phone numbers in the comments field. You can find more information on validating phone numbers in this related topic. Hopefully this will help to prevent validation errors.