(soccer) explore.py gives a stationary frame of the pitch?

Hi, thank you for releasing the code of this fantastic project!

I tried to run the explore.py given in the repo (dm_control/locomotion/soccer/explore.py). However, it seems that the GUI that pops up only renders one stationary frame and nothing is moving. Should I interact with the players using keyboard inputs or load some pretrained policies? What should I do?

I have recorded a 15-second short [video](https://drive.google.com/file/d/1cllPjn2JVxMOKnvF1LdNAxFhh789qT0O/view?usp=share_link) of what happened when I run the explore.py in the command line.

Thanks a lot for any suggestions!!!