Microsoft open R fatal error when trying to change number of core for multithread processing

Question

I am using window 10 pro and downloaded Microsoft open R to run in rstudio. open R has built-in multithread processing I want to try out.

I tried command setMKLthreads(2). then R shows fatal error and needs to restart.

when I run the getMKLthreads() R is running fine

getMKLthreads() [1] 8

only when I want to change the number of cores R collapse.

Please advise