Hi @v-shex-msft, thanks for replying. It was a good idea to move the folder around the computer, as the Documents folder was linked to OneDrive. After relocating R to C:\R\R-3.3.3 (also trying an older version), a new error presented, claiming permission was denied.
This might have become a similar problem to this, where antivirus software was preventing Power BI from accessing R.
Edit, confirmed. After checking event logs in antivirus software, Rscript.exe was prevented from accessing the RScriptWrapper.R file as executing scripts are blocked in this organisation.
Edit2: It actually works when published online!, including the usage of a version of ggplot2 incompatible with R~3.4.4. So clearly there's a difference in how R Script visuals process bewtween Power BI Desktop and Power BI service.