I had raised this question last month here leaving it for further observation but it remains to be solved.
Update is that I have changed my mac, with a brand new downloaded new chrome browser but the problem persists. Seems it is the Rstudio version on Ubuntu 20 that is having a bug.
Here is a recent screenshot showing the problem.
Note that there are two popups and the first one masks the second. Is this an rstudio bug or just a configuration change that can fix it. I very much need the second popup to be clear enough as it contains the function argument help text.