Observation about seat assignments and change of seat assignments (it looks like amadeus doesn't reflect update information about seat assignments):

I got the Amadeus code and the KLM code from the travel agency for a booking with 4 segments. I was able to check the itinerary on checkmytrip.com with the Amadeus code and on the klm.com with the KLM code (AFAIK, klm.com shows no info about seat assignments). So far so good.

Unfortunately, the travel agency did not assign my preferred seats so I went to a KLM ticket counter where I was able to change all seat assignments. The KLM ticket agent used the KLM code.

Now I went again to checkmytrip.com and I still see (it's now already 2 days later in case a delay may be possible to show the change) the original seat assignment. So I asked in a KLM lounge to check my seat assignments. The agent used again the KLM code and told me the "preferred" seats.
I also checked on www.seatmap.com . The seatmap viewer shows the original seats as occupied (ok, it could be possible that anybody else got the same seats on all of the 4 segments - but I think it's somewhat unlikely). The seatmap viewer also shows the seats I'd like to get as occupied .