nexct cloud update problem

There is a hidden file named .step somewhere in your Nextcloud install. Search for it in command line and back it up somewhere else and remove it from where it is.
find /sharedfolders/ -name ".step"
That will enable the update to restart. There is an underlying problem and it will probably hang on Step 4 again. Try this though to see if it acts accordingly.

I had this same problem just two weeks ago when I attempted to upgrade from 17.0.0 to 17.0.1. I think there was a permission problem with one of the folders in the Nextcloud install. I have scanned my search history and cannot find the pertinent information. Type the following in your command line and see if there appears to be anything that looks out of place with ownership or permissions. Start with /sharedfolders then check /sharedfolders/AppData and /sharedfolders/Nextcloud.
ls -l

Additionally, you might have a look at Updating Info in the Docker Info page for Nextcloud. I'm sorry I can't be more specific because I cannot remember exactly what I did to fix the problem. I may find out here in a bit because I need to update from 17.0.1 to 17.0.2. Maybe someone else will chime in and have the fix.

Yes, but the OP is stuck on step 4 of the update process. The update refuses to go beyond step 4, I think because of some kind of folder permission issue. Where did he go, anyway?

Well, the OP vaporized. If anyone else finds themselves stuck in the Nextcloud update issue mentioned in the first post above, having just now attempted to update from 17.0.1 to 17.0.2 (and failed), I remembered what caused the upgrade to hang at step 4 and it was indeed a permission issue. I ran ls -l for my /sharedfoldes and found that my AppData folder was indeed owned by root instead of my docker user. My Nextcloud folder being created from a docker-compose.yml file was created (and owned) by my docker user already. I merely changed the ownership of my AppData folder to my docker user and re-ran the update. The update from 17.0.1 to 17.0.2 completed successfully.