Sorry for the disruption, our engineers have just finished publishing a fix for this. If you are on the CSD mailing list you should have received an email from me earlier this morning - content pasted below:
If your students are currently working on CS Discoveries Unit 3, please read below.
We received several reports from teachers this morning about some of our Game Lab levels that involve animations. Students may be seeing a dialog like below when loading a level:
We are feverishly working on a fix and should have this issue resolved in the next few hours (ETA by 12pm PST). Completing these levels will not be possible until this issue is resolved.
Once this issue is resolved, students should be able to complete this lesson as normal. If students have clicked on the “Delete” button, they should be able to use version history to go back to the last working version and try again.
We are very sorry about any inconvenience this issue has caused for your classrooms and know that we take these issues very seriously. Thank you for your continuous feedback and support in helping us to improve.