Already 5 senior designers have been trying to fix this issue, and we believe it doesn’t come from our end. When running a prototype, the bottom bar is supposed to be fixed but its position keeps changing. There is no logic : it can be ok or not on 2 same devices, and it can be ok or not depending on the moment you launch it. Plus, it affects prototypes that were working perfectly fine one week ago. → Hence we feel the problem comes from Figma.
One thing to add : this affect only the visual layer, because the interaction cues are in the exact position.