sleuth56 That's not how updates work at all. You can skip over any number of releases. Delta updates are an optimization shipping only the changes from one release to another which are used by the update client when available. You're downloading the full update packages with the entireOS. There's no reason you need to install every one.
Sideloading will show an error message if it fails. Is your device locked? If it's not locked, you may not actually be on a fully complete GrapheneOS install with no modifications. It sounds like you're sideloading an update, trying to boot it and it's failing to boot for some reason like that and triggering rollback which you haven't been noticing.