ParticleEmitters using a flipbook have their rate slightly changed (but still really visible) by the distance between the camera and the ParticleEmitter parent 3D object (part/attachment).
http://gyazo.com/be37751b072b36801fe93406fde497fc
In that Gyazo video you can see how (on both ParticleEmitters, blue and red ones), if camera close to the ParticleEmitter, particle gets brighter for a moment (which means overriding; which obviously means a higher emitting rate than particle lifetime); at the same time, if I get my camera away, we can observe a moment of absence of particles (which means a lower emitting rate than particle lifetime).
Expected behavior
Flipbook particles should have the same rate/lifetime always, no matter where the camera is located at.