TAB in console completion triggers error

In rstudio, I continue to have problems with completion.

For details, please see: When typing in Console (in RStudio) repeatly get error 'attr' error msg.

As suggested, I moved various rstudio config files to backup. I also set completion to 'never'

But in console, if i type beginning of "library" and hit TAB,
the same error appears above it.

**Error in base::attr(..., exact = TRUE) : **
**  formal argument "exact" matched by multiple actual argument**s
librar<TAB>

Likewise if I type even one letter and then TAB, the error triggers.

l<TAB>