Geo: output to geo.log just stops for long periods of time

Consider this graph:

Screenshot_from_2017-09-18_16-33-16

On both on the 14th September and the 17th September, a long period of no Geo log output is seen. What's causing this?

Broken geo_log_cursor? Broken sidekiq? Something else?

/cc @dbalexandre @jarv