Thanks @seiriosPlus . I hit into the same problem deploying an app to heroku. I haven’t encountered the problem before with the app - hit into it after updating to streamlit 1.13 & python 3.9.15.
Your solution worked after all other suggestions failed (e.g. <1> can’t update the filesystem on heroku so not possible to update max_user_instances and max_user_watches; <2> Setting fileWatcherType = “none” in the [server] section of config.toml didn’t have any effect 
).
Thanks again for your suggestion!