Seen in gh-30160
@mattip reported seeing this independently too

Basically, the test (sometimes) fails as

FAILED numpy/linalg/tests/test_linalg.py::TestQR::test_stacked_inputs[float32-outer_size2-size1] - RuntimeWarning: invalid value encountered in matmul

I'm able to reproduce this locally (although unreliably), so I'll attempt a bisection.
possibly related to gh-29820