javascript function changes when used with jakarta ee

I am starting my long and bumpy road to move website from shit i made 20 years ago to Jakarta ee backend, mysql and html javascript frontend. Have some success with java, but problems in javascript.

In my JSP I have javascript function to make thumbnails (chatgpt helped me):

// Generate thumbnails and add click event listeners
                imageData.forEach((data, index) => {
                    const thumbnail = document.createElement('div');
                    thumbnail.classList.add('thumbnail');
                    thumbnail.innerHTML = `<img src="${data.url}" alt="Thumbnail ${index + 1}">`;
                    thumbnail.addEventListener('click', () => displayImage(index));
                    galleryContainer.appendChild(thumbnail);
                });

Localy it works fine, but when it comes back from tomcat fifth line is truncated:

                // Generate thumbnails and add click event listeners
                imageData.forEach((data, index) => {
                    const thumbnail = document.createElement('div');
                    thumbnail.classList.add('thumbnail');
                    thumbnail.innerHTML = `<img src="" alt="Thumbnail 1">`;
                    thumbnail.addEventListener('click', () => displayImage(index));
                    galleryContainer.appendChild(thumbnail);
                });

what could be wrong and how to avoid it?

I expected that jsp content would be the same, only with added image list (which works fine).