JWT token seems to be changing between "before all" and first test in Cypress

I am running the following test on Cypress

before(() => {
      cy.horizonAuth()
      cy.log(sessionStorage.getItem('JWT'))
    });

//API requests

    it('Sending a regular API request to Welcome Messages', function() {
        cy.log(sessionStorage.getItem('JWT'))
        cy.request({
            method : 'POST',
            url : '/api/v1/organisations/welcome-message?actions=api/v1/organisations/welcome-message/set-welcome-messages',
            body : {"welcome_messages":[{"message":"<p>Test investor welcome message!</p>","type":"User"},{"message":"<p>Token from storage </p>","type":"Internal User"},{"message":"<p>Test entrepreneur welcome message!</p>","type":"Entrepreneur"}]},
            auth: {bearer: sessionStorage.getItem('JWT')}

    })
})

This is the auth command I am using

Cypress.Commands.add('horizonAuth', () => {
    let config = Cypress.config();
  
    cy.request({
      method: 'POST',
      url: Cypress.config('tokenUrl') + '/api/v1?actions=api/v1/login',
      body: {
        username: config.horizon.username,
        password: config.horizon.password,
      }
    }).then(response => {
        cy.setLocal
      window.sessionStorage.setItem('JWT', response.body['api/v1/login'].token)
    })
  })  

I noticed that my tests were failing the first time I ran the above, but if I ran the test a second time and commented out the cy.horizonAuth() then the test would pass. I decided to add the log commands to see the JWT token and it appears that the token is changing between the horizonAuth and the first test. This happens if I close the session and start a new session also as the first time it's run the Log comes back with "Null"

Any help on this would be greatly appreciated as I am fairly new to Cypress.