Mac OS Catalina 10.15.4 - Rstan: Execution halted

Hi
I’m using rstan and brms in Rstudio, and as I recently updated to Catalina 10.15.4,
there were some issues, first I had to install Xcode from the App Store (a window pops up and says I have to “Install Build Tools” see full text below), then after initialising something the process breaks down.

So after doing stan (…) it prints in the R console:

starting worker pid=3966 on localhost:11834 at 12:28:30.404
starting worker pid=3965 on localhost:11834 at 12:28:30.403
starting worker pid=3964 on localhost:11834 at 12:28:30.408
Error in unserialize(node$con) : error reading from connection
Calls: -> slaveLoop -> makeSOCKmaster
Error in unserialize(node$con) : error reading from connection
Calls: -> slaveLoop -> makeSOCKmaster
Error in unserialize(node$con) : error reading from connection
Calls: -> slaveLoop -> makeSOCKmaster
Execution halted
Execution halted
Execution halted
*Error in makePSOCKcluster(names = spec, …) : *
Cluster setup failed. 3 of 3 workers failed to connect.

Short session info:
R version 4.0.0 (2020-04-24)
Platform: x86_64-apple-darwin17.0 (64-bit)
Running under: macOS Catalina 10.15.4

And the window when I first do stan(…) is:
Install Build tools
Building R package from source requires installation of additional tools.
Do you want to install the additional tools now?

Can anyone help/direct me to the right person or place? Any idea highly appreciated.
Best
Giuachin

It is a bug with RStudio when working interactively.