F1 model

I generated a 60 seconds of a person. During this time the person changed a lot visually (including body type from chubby to slim). Its not the same person anymore. Not sure if this is related to F1 to be honest.
Also the lighting and colors have changed a bit.

Start by reproducing the reported 60-second generation with the F1 model and inspect whether the person's identity, body type, lighting, and colors change over time. Determine whether the behavior is specific to F1, then document the cause or provide a confirmed fix and reproduction details.

Written by the indexing model from the issue text.