Bangle2 died on low power - did not shut itself down?

Unfortunately I did not make a picture of the screen. It was definitely not connected to temperature as I was inside the whole time and the temperature-value (displayed as part of my LCARS watchface) always showed 30-33°.

But I can describe my actions and what I observed:

• start at normal LCARS watchface, locked. no visible distortion.
  
• press button. lock widged disappears
  
• press button. "loading" box appears for a bit then the upper ~1/4 of the screen looks like the Settings/Launcher menu but with small quirks here and there. Below that a part of the "loading" box remains a bit distorted and on the remaining screen there are partly color spots/leftovers from the LCARS watch and partly stripes/dots that look like from the Settings/Launcher menu.
  
• press button for 2s. In the middle of the screen some movement and 1 or both vertical lines for the "loading" box appear, but only part of the content.
  
• no matter what clicking or touching the screen I did it stayed corrupted.
  
• after ~2-3mins the screen recovered and showed the LCARS watchface again properly.