It is highly UNlikely that in case of a Pi (operating system related) problem like yours the UI (and reboot button) would have been unaffected, i.e. you would not have been able to access the UI or the reboot button would not have worked anyway. Don’t waste your efforts on this, you’ll just get disappointed.
Go debug your Pi, probably easiest is to reinstall right away with a focus on minimizing writes to SD, see here for tips.
