I have noticed this warning running R snippet node: WARN R Snippet 0:34:0:18 R Version 3.5.0 and Rserve <= 1.8-6 currently have issues preventing their full use in KNIME. A future release of R and/or Rserve may fix these issues.
Is it a generic warning or connected to code that is inside? What can not be full use? If used will node give an error or wrong result?
I have seen various behaviours on different machines. From just giving this warning to refusing to work to some very strange warnings on a windows server about possible data leakage and a stopped Loop (the loop using R nodes).
So I would highly recommend making the update. Unfortunately there is no binary version of the package there yet so you would have to compile it yourself which might need additional packages on Windows and MacOS for example. I struggled with a windows compilation for some time because the installation is rather picky with its paths (does not like blanks and stuff).