Check out your edit function. When multiple cars are in the models list, edit button will return carDetails by the car that has been added as the latest item - but not the actual car of the given event itself. Move carDetails into the publishBtnEl eventListener (closure) and code gives 100%. 

function solve() {
    let inputElements = document.querySelectorAll('fieldset input, select');
    let publishBtnEl = document.getElementById('publish');
    let tableBodyEl = document.getElementById('table-body');
    let soldCarsListEl = document.getElementById('cars-list');
    let totalProfitEl = document.getElementById('profit');

    // let carDetails = {};
    let totalProfit = 0;

    publishBtnEl.addEventListener('click', (e) => {
        e.preventDefault();

        let carDetails = {};

        let hasEmptyInput = Array.from(inputElements).some(x => !x.value || x.value.trim() === '');

        if (hasEmptyInput) {
            return;
        }

        Array.from(inputElements).forEach(x => {
            carDetails[x.id] = x.value;
        });

        if (isNaN(Number(carDetails['original-cost'])) || isNaN(Number(carDetails['selling-price']))) {
            return;
        }

        if (Number(carDetails['original-cost']) > Number(carDetails['selling-price'])) {
            return;
        }

        let trRowEl = document.createElement('tr');
        trRowEl.classList.add('row');

        Object.keys(carDetails).forEach(key => {
            let tdEl = document.createElement('td');
            tdEl.textContent = carDetails[key];
            trRowEl.appendChild(tdEl)
        });

        let tdBtnsEl = document.createElement('td');
        let editBtnEl = document.createElement('button');
        editBtnEl.textContent = 'Edit';
        editBtnEl.classList.add('action-btn')
        editBtnEl.classList.add('edit')
        let sellBtnEl = document.createElement('button');
        sellBtnEl.textContent = 'Sell'
        sellBtnEl.classList.add('action-btn');
        sellBtnEl.classList.add('sell');

        tdBtnsEl.appendChild(editBtnEl);
        tdBtnsEl.appendChild(sellBtnEl);

        trRowEl.appendChild(tdBtnsEl);
        tableBodyEl.appendChild(trRowEl);

        Array.from(inputElements).forEach(x => {
            x.value = '';
        })

        editBtnEl.addEventListener('click', (e) => {
            Array.from(inputElements).forEach(x => {
                // console.log(carDetails);
                x.value = carDetails[x.id];
            })

            tableBodyEl.removeChild(trRowEl);
        })

        sellBtnEl.addEventListener('click', (e) => {
            let liEl = document.createElement('li');
            liEl.classList.add('each-list');

            let carModelAndNameEl = document.createElement('span');
            carModelAndNameEl.textContent = carDetails.make + ' ' + carDetails.model;

            let yearEl = document.createElement('span');
            yearEl.textContent = carDetails.year;

            let profitEl = document.createElement('span');
            profitEl.textContent = Number(carDetails['selling-price']) - Number(carDetails['original-cost']);

            liEl.appendChild(carModelAndNameEl);
            liEl.appendChild(yearEl);
            liEl.appendChild(profitEl);

            soldCarsListEl.appendChild(liEl);
            totalProfit += Number(carDetails['selling-price']) - Number(carDetails['original-cost']);

            totalProfitEl.textContent = Math.round(totalProfit).toFixed(2);
            tableBodyEl.removeChild(trRowEl);
        })
    })
}