throw new Error("Unknown UI mode"); - when selecting Vertical Clock as default clock.

Yes - I updated all apps that said they were out of date, which at the time was those 3.

The issue is indeed with Vertical Clock which appears to be broken now - maybe nothing to do with bootloader or the settings app.

I only noticed as I used it to look at something else and used Vertical Face to test something.

@Gordon - I can see you did a change in commit a4358600a0791e17cc5978c9ae0d08b0a584e6b4

Author: Gordon Williams gw@pur3.co.uk
Date: Mon Jun 28 11:13:47 2021 +0100

verticalface 0.09: Fix time when minutes<10 and hours>9 (fix #767)

which introduced

Bangle.setUI("clockupdown", btn=>{