(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!!!

Start by running dm_control/locomotion/soccer/explore.py and compare the result with the reported stationary frame and linked video. Read the script to determine whether keyboard input or pretrained policies are expected, then clarify the required interaction or document the reproducible issue and its expected behavior.

索引モデルが issue の本文から書いたものです。