Hi, I am in no way an expert as I’ve just been learning brms and Stan but I had a similar error after I tried to update brms and @andrjohns gave me this advice:
Compile packages using all cores
Sys.setenv(MAKEFLAGS = paste0("-j",parallel::detectCores()))
install.packages(c(“StanHeaders”,“rstan”),type=“source”)
Stan post error code
I’ve included the link to the original post. Once again, I’m no expert and don’t want to be giving you incorrect advice, but seeing no one answered and how similar it looked to my error, this might be worth a try.