Thank you all for your replies. The request for package version prompted me to run updates to see if that would fix things. Package updates didn't fix the matter, but an update to R version 3.5.3 did fix it.
I'm still not sure what caused the original error but I guess the lesson for me is to keep running updates.
Just for thoroughness, I'm showing the correct output (from the exact same script) and have added the sessionInfo as well. Thank you all again.
