How did you install/build OpenBLAS? The slow-down in “local system build & factorizarion” could probably be attributed to differences in the LAPACK routines. For MacOS it might be worth linking with the Apple Accelerate library instead (with gfortran you just have to add -framework Accelerate).
A slow-down from 1.6 to 2.8 seconds, doesn’t seem like the end of the world. I imagine your true computations are much bigger than this?