This proactive topic aims to foster knowledge of the Shipping module of the VTEX platform here in the community! 
Questions like these are common and we have complete documentation that explains the six most common scenarios in which this situation can occur and their respective solutions:
With that in mind, the goal of this topic is simply to translate that documentation into everyday platform use and show how to identify the scenarios outlined in it.
1. Competition between carriers of the same type
To identify this type of issue, a simple option is to run a Shipping Simulation, because doing so will display the following message:
Reason: Disregarded due to priority.
This means that Carriers A, B, and C will not be considered at checkout — only Carrier D. In addition, the checkout displays the shipping methods (in this case,