Upgrading without sudo/root isn’t possible. That cannot be the issue.
Upgrading can cause issues but should not. If that was to happen, then many users would report the same issues. Upgrading is important.
Given the situation, for Whonix 16 stable release of consider Whonix 16.0.0.8 (Debian 11 bullseye based) - for VirtualBox - Major Release - Testers Wanted!.