I met the issue in both TF-M 1.3 and 1.4. The default "PS_NUM_ASSETS" is too small to be practical, so I enlarge it to e.g. 45 from 10. Then I run regression tests, but TFM_SP_PS_TEST test fails. Per my guess, stack is the point. So I enlarge TFM_SP_PS_TEST stack from 0x500 to e.g. 0x800 in tf-m-tests/test/test_services/tfm_ps_test_service/tfm_ps_test_service.yaml. Re-run regression tests and TFM_SP_PS_TEST test passes this time.
I think the configured stack size of TFM_SP_PS_TEST can be larger to accommodate larger 'PS_NUM_ASSETS' configuration. The increased resource usage can be less concerned due to only for test.