I believe the bug is caused by a temporary unstable connection to steam server (according to the error code).
It was fixed in a silly way: Ignore the error message and keep playing without connecting to steam API.
(At the cost of not unlocking achievements. Achievements will be unlocked the next time game successfully connected to steam)
I am still reading the documents at the moment, trying to figure out a better solution.
Other stuff:
Level 9-? reworked.
I'm working on a chapter 12 update. It will be available before Christmas.
12.9. update:
Found a better solution.
Achievement should work again.