Yes, and the explanation is given at the github page. However, if you set threadcount to 1 (test.nim, line 14), such messages should never occur.
> Unfortunately writing fast and correct concurrent data structures is an > extremely hard problem. > ([https://forum.nim-lang.org/t/6070#37565](https://forum.nim-lang.org/t/6070#37565)) and testing them is hard, too...