If extraction fails at part 19, use WinRAR or 7-Zip to "Test" the archive. You may need to redownload just this part if it's corrupted.
The community often hunts for "impossible to find" cars, like the 2022 BMW M5 CS or the Aventador SVJ , which are usually only obtainable via the Auction House. Forza.Horizon.5-CODEX.part19.rar
If you are having trouble with this specific part or the overall installation: If extraction fails at part 19, use WinRAR