Holiday Challenge Bug
This has happened to me twice now, once on Day 1 of the Holiday Challenge, and once on Day 2 (so far - the day is young).
Both times it was while running a challenge event in the Desert node.
The first sign that something was wrong was that many of the blocks were not being destroyed even when my TF's weapons fire clearly hit them. Then he arrived at the black space and couldn't progress any further. The only way to get out of the event was to exit back to the map or to hard close the app.
See picture here:
On both occasions, when I went back to the Holiday Challenge screen, I had lost the event "charge" that I used to start that event, so I'm down an event on both days.
@gradientturtle7