Fix for MLD difference observed with few files

[x] Includes fixes in the function in_tri_fixed() for improving precision.

Test results:
pytest results:
pytest-mld-dec: 573 failed, 1 passed, 381 skipped
pytest-mld-dec-lev-10: 573 failed, 1 passed, 381 skipped
pytest-mld-dec-lev+10: 573 failed, 1 passed, 381 skipped.