Hi, this method works, I always use it since the last previous fast ring builds are having problems installing/downloading through Windows update:
use this website: https://uupdump.ml/known.php
select your build number
select language and click next
select the right edition and click next
then click on "download using aria2 and convert"
after that extract files to a folder and run the "aria2_download_windows.cmd" file.
wait for it to finish, once it's done it will create a complete and official ISO files which you can use to install your next Windows insider build without any problems.
remember it's all OFFICIAL and it downloads directly from Microsoft servers.