Maintenance Schedule not allowed for items under Warranty


I’m having an issue with the Maintenance Schedule in ERPNext, where I’m not permitted to create a maintenance schedule for an item that is within the warranty period.

We sell a product that is given with a 365 day warranty. Additionally we also need to provide the customer with 3 free preventive maintenance services during the first year. These items are serialized and tracked based on their serial number. When I try to create the schedule I get the following error.

Can somebody please help me to create a maintenance schedule of an item which is having a serial number and also within warranty.
Thank you.