Don’t keep hammering Download from the same draft. If the preview and exported file are pulling from different saved states, every download will repeat the same bad version.
@fusionarchitect7238p may be right that it’s an export bug, but first check whether your edited text was actually committed. Some editors update the preview immediately while you type, then send the last saved caption to the export server. Click outside the text box, press whatever Done or Apply button is available, and wait for any saving indicator to finish. Then refresh the page. If your exact wording survives the refresh, download it. If it changes after refreshing, the problem happened before export.
I would prefer a clean duplicate of the content rather than the one already on the meme. Paste the caption in a plain text editor, make a new meme out of the same template, put the lines into their respective fields, and note the changes.
It is important to not load an old draft, or go back in the browser history, or restore a previous session, because those can leave you with the image that was already saved by the website.
Make sure to note if the prompt, the top-text or the bottom-text were replaced as well. If the replaced text was in the caption, or the prompt was taken from the suggested captions, then it is very likely that the exporter read the wrong part of the project. If the text was not taken from the fields of the current meme, but rather it was newly composed, then the exporter most likely uses the image generation/researching/updating tool as well.
Save the preview, and the downloaded version, and report the exact process that had to be done for the issue to occur. Report if the text changes upon refreshing the page, or only after the image was downloaded. This is important, so the developers know, whether they have to research the draft saving/loading, the versioning of projects, or the rendering of the images, rather than an unrelated issue, of the AI changing the meme.