This sequence: U+120B,U+135F,U+120B with the Nyala font from Win7
exposes a GPOS bug in Uniscribe, in that the positioned mark is wrongly
moved as a result a following kern.

This is the one "failure" in the Ethiopic test suite :-).

ETHIOPIC: 118900 out of 118901 tests passed. 1 failed (0.000841036%)