Vertical slat parquet – Are the joints properly filled? Is the sanding correct?

Dear everyone,

I hope you can help me. We recently got a new vertical slat parquet. It has already been filled, primed, and coated once with lacquer. Tomorrow the next lacquer layer is due.

Unfortunately, I have to say that the joints don’t seem to be filled correctly. The filler has sort of “sunk” into the joints and is not flush with the top edge of the slats. There are many small canyons, and some joints also seem not properly filled. Moreover, the transition to the tiled floor is not particularly well sanded; it is a mountain-valley wave landscape.

Was it filled correctly like this? Can you not expect a better result? The same applies to the sanding. It has to be better, right?
Thanks in advance for your tips and experiences!

Tom

Please upload images that show the overall situation. Always these "meaningless" macro shots :-(
The third picture looks to me as if the apprentice lost control of the grinding machine; I can't explain the grinding marks otherwise.

If I were to do it myself, I would follow a recommendation from my carpenter and fill the joints with a paste made from the sanding dust of the floor mixed with the lacquer to be applied. Or with an approved filler. Here it looks as if this has shrunk and therefore settled into the joint. If you look at the entire floor (good image quality please), you can probably assess it better. Maybe then as a floor specialist could take a look?