When creating a JIRA instance from scratch, the following priorities are created by default:

If we create one issue with each priority and search for issues, they are correctly retrieved.

However, if we rename the priorities for numbers, and those numbers are the IDs of other priorities, JIRA will search for the IDs and not the priority names, bringing inconsistent results.

For instance, If we search for priority name "High", it will bring issues with priority set to "High".
Let's say we edit the priority names to the following:

If we search for priority name "2" (which was the High priority in the first example), it will bring issues with priority "ID" 2, not consistent with the expected results, since in the screen we select the priorities according to their names: