I have encountered this problem while using R on buster. 1. From main install from R with packages "caret" and "pls" 2. From non-free install libmkl-full-dev. When prompted confirm to use MKL in BLAS/LAPACK/ETC. Train some statistical model using caret with method pls. The results are drastically different (worse) when using MKL. After uninstalling MKL things went tot normal.