Hi Ryk Kleynhans,
Since the common save-location, update, add-in, and document checks have already been covered, I suggest trying an Office Online Repair next. Please try the following steps:
- Open Settings > Apps > Installed apps.
- Locate Microsoft 365/Office, select the three dots > Modify.
- Run Online Repair, then restart Word and test saving again.
If the issue continues afterward, please share whether it affects new blank documents as well as existing documents. That will help narrow down whether the problem is document-specific or related to the Office installation.