autoFill extension returns NaN instead of incrementing

[JasperSch]

This issue is due to problems in the underlying packages and has been reported:

rstudio/DT#1123

https://datatables.net/forums/discussion/78109/bug-is-it-possible-to-fix-incremental-cell-dragging-autofill-extension#latest

As a temporary solution, you can use an earlier version of DT:
remotes::install_version('DT', '0.30')