A big thanks for the video. It looks very much the same as mine. However I cannot get the result he's getting.
The battery for the chronometer watch(closer to the front of my hand once I wear it), he manages to fit it in by pushing/sliding the battery in. In my case, the batter sticks out from the holder from the side closer to the centre of the watch. There is a little bar passing over the edge closer to the side of the watch, once I slide in the battery underneath of that bar, the edge closer to the centre of the edge, has no holder or fit which keeps it in place.
For the other batter (for the watch closer to my elbow), there is a screw he's loosening then tightens once battery is in place. In my case, the battery doesn't seem to be fully fit in place. So tightening of that screw doesn't help.