Error "The product and the unit cannot be updated while the entity is locked" when creating Order Product

Hi everyone,

I'm trying to create a new Order Product from an active Order but when i try to save it with all the required fields filled it throws the error "The product and the unit cannot be updated while the entity is locked". Do you know how can i solve this to be able to save that new record? 

I've seen the following refers that are not working in my case:

https://community.dynamics.com/crm/f/117/t/226502 

https://community.dynamics.com/crm/f/117/t/149832 

Thanks :)