After editing a single event in a recurring event series, the Previous and Next buttons for navigating to past or future instances stop working. The UI shows that the event is still part of the recurring series, but the buttons are disabled:

This happens for example when rescheduling a meeting.

1. Create a recurring event.
2. Use previous/next buttons to navigate between instances.
3. Reschedule one instance of the event to another start time.
4. Previous/Next buttons don't work anymore.

phabricator d3b7a0f37c975397455d633254e9b4a1246023f9 (Sat, May 27) (branched from 9d37ad3022bfff8a2900b9d728e6abbb6a1e27f0 on origin)
arcanist 21fe07925b07cab0f73ec824fe8ce02f53b24fe0 (Sat, May 20) (branched from 129d51fa0936c9bae48fadf3a3f39e26d69d24da on origin)
phutil d02cc05931b02c684d4c729510090591ca45f951 (Apr 29 2017) (branched from a900d7b63e954e221efe140f0f33d3d701524aae on origin)