As noted in Bug 204485, when U_OTHER_NEUTRAL is encountered in createBidiRunsForLine at the end of a run, the result is unhandled. There are perhaps other cases of other rules with regards to resolving neutrals as part of UAX #9 (https://unicode.org/reports/tr9/#Resolving_Neutral_Types) which may also need additional handling.
<rdar://problem/57604704>
*** Bug 188406 has been marked as a duplicate of this bug. ***