Hello, I would like to call to your attention this issue on SO:
https://stackoverflow.com/a/70240075/2203727
Because RStudio gathers metadata for the "Environment" pane, the iterator is consumed by this process and results in faulty execution in the console. The reporter, Mikael Jagan, says that implementing a str function or refactoring the as.list function may resolve this issue.
In the meantime, turning on the "Manual Refresh Only" setting works around the issue.