Ever since the maintenance break and update, I've got occasional errors on the app when I try to progress. Usually if I try again, I'm able to proceed.
This morning when I tried to get the free chest of gems that you can get once an hour on the app, I got an error message that something went wrong and that they were awarding me some gems anyway.
Last night, after I got to a point on the snake where you can open a chest of gems, I opened it and tried to proceed to the next lesson. I was informed that I had to complete the earlier lessons that I had already just completed to proceed. I switched to a different language and when I came back I got awarded a second chest of the same gems on the snake path (usually not possible) and was able to proceed.
I think I've seen a few other glitches here and there. I'm guessing there may have been some coding errors when they did the update.
Didn't take any screen shots that would offer information on what happened. I took one screen shot of the Spanish snake at the point where the error occurred, but looking at it now, there's nothing unusual to give a clue what happened.