I have a persistent multiple warning of "unknown column" for all types of commands (e.g., str(x) to installing updates on packages), and not sure how to debug this or fix it. 

The warning "unknown column" is clearly related to a variable in a tbl\_df that I renamed, but the warning comes up in all kinds of commands seemingly unrelated to the tbl\_df (e.g., installing updates on a package, str(x) where x is simply a character vector).