My best guess is you are installing from an older version, and it looks like maybe the script is running through each newer version and installing it before installing the following version, until it gets to the current version.
We’ve now had a second person report this problem:
Please post your issue to GitHub.
I did just notice there seem to be different repositories for Nextcloud. MiaB 56 is using nextcloud-releases instead of the official Nextcloud. Previous versions of MiaB (including 55) used the Nextcloud repositories.