Thanks, @paul.buerkner. I have a brmsfit object that took hours to finish and I was hesitating to restart the session but it seems I have to. Therefore, I will try closing everything and see what happens. Also, just found this solution
adding
-flto -ffat-lto-objectstoPKG_CPPFLAGSin src/Makevars.win
to a similar problem, so I will also try to implement this solution proposed by @bgoodri and see if I get this problem solved. Otherwise, I will let you know.