Hi, I am suddenly experiencing a similar problem in v 2021.1.3, but it is with initCodeJS instead of writeRoutineBeginCodeJS.
I have already synchronized this project a few times without issues, and this time I just wanted to push a small change in the slider width; something I’d already done.
EDIT: I found the problem; see this thread: Error syncing "TypeError: __str__ returned non-string (type NoneType)" - #7 by aisa2