How do I make a Cypress Alias work between test cases?

I am getting inconsistent behaviour when using aliases in Cypress. I think it may be down to something with asynchronous behaviour between test cases.

From the Cypress documentation I tried both methods of referencing the Alias.

With 'this'

    it(`When clicks on an entry from the list`, () => {
        cy.get(`tr`)
            .eq(2)
            .within(() => {
                cy.get(':nth-child(1)')
                    .invoke('text')
                    .as(`etaId`)
                    .then(() =>
                        cy.get(':nth-child(1)')
                            .click()
                            .then(() => cy.wait(100))

                    )
            })
    })

    it(`Then ETA details are shown`, () => {

        cy.contains(`ETA: ${this.etaId}`)
            .should(`be.visible`)
    })

Gives the error

Cannot read property 'etaId' of undefined

With 'cy.get(@{alias}).then()'

    it(`When clicks on an entry from the list`, () => {
        cy.get(`tr`)
            .eq(2)
            .within(() => {
                cy.get(':nth-child(1)')
                    .as(`etaIdCell`)
                    .invoke('text')
                    .as(`etaId`)
                    .then(() =>
                        cy.get(':nth-child(1)')
                            .click()
                            .then(() => cy.wait(100))

                    )
            })
    })

    
    it(`Then ETA details are shown`, () => {
        cy.get(`@etaId`)
            .then(id => {
                cy.contains(`ETA: ${id}`)
                    .should(`be.visible`)
            })
    })

I know that the selector for the alias is correct because the following code when I do everything in the same test case works correctly

      it(`When clicks on an entry from the list`, () => {
        cy.get(`tr`)
            .eq(2)
            .within(() => {
                cy.get(':nth-child(1)')
                    .invoke('text')
                    .as(`etaId`)
                    .then(() =>
                        cy.get(':nth-child(1)')
                            .click()
                            .then(() => cy.wait(100)
                    )
            )
        })
        .then(() => {
            cy.get(`@etaId`)
                .then(id => {
                    cy.contains(`ETA: ${id}`)
                        .should(`be.visible`)
                })
        })
    })

and I can see in the dev tools

I would appreciate any help.

Thanks