Hi @learningR5! Welcome!
Can you clarify which version of RStudio you have? There are currently a few different versions that could be considered “latest” — the current 1.1.x release, the current 1.2.x Preview release, or even a bleeding-edge 1.2.x Daily release.
A few initial thoughts:
Does the file saving problem only happen for .Rnw files, or do you also see it when trying to save other types of script files?
Is there anything unusual about your computer setup? Is your working directory (or your user directory) on a network drive?