Sorry Enkonyito, I should have better tested the changes I made for video generation in the version 1.1 of the YafaRay plug-in. The issues should be fixed in version 1.2 that I tested by rendering images more than once with a camera time and place change between frames.
You'll see that I also added to YafaRay some methods able to remove lights, backgrounds, integrators and cameras, to prevent the need to restart YafaRay engine between two frames.
Hope you can integrate these changes more easily in your plug-in.