Something else that might be helpful to know here:
Did you freshly install RStudio after buying your new laptop? Or did you transfer the installation over from an older computer? What version of RStudio were you running on Mojave, and what version are you running now?
I suspect it will ultimately be difficult to resolve this unless you’re game for upgrading your OS again and giving it another try. No patch on the Apple support person, but I wouldn’t expect any OS support staff to be familiar enough with (ultimately rather esoteric) software like RStudio to be able to help much beyond “this application here is having a problem”.
But if you can figure out how to recreate the problem and run RStudio’s diagnostic tools while it’s happening, it’s possible RStudio folks here might be able to see what’s going wrong. If there is an identifiable bug, figuring that out would be helpful for everyone.