Yes, This is always a concern with any devices. I agree that It is good to get to the bottom of it. @NoWon go all the trouble of starting from scratch and add up one device at a time to find the offending device. It is an example of how to find the issue. This is one way of finding a conflict. Another is as suggested by @NoWon, you can analyze the graph and look for potential issue by looking the neighboring devices. I would not want you to reconfigure your devices for this effort if it is not possible. However, it may not be possible to do without "process of elimination" troubleshooting. In any case, I hope you can find the issue without blowing up your network.
Yes. I am more concern about the packet drop. They are excessive compare to what I observe. I have a lot of these sensor obviously. They are not even close to see what you saw with yours in packet drop department. I have one router that has been up for 3 months. There is not a single drop on that one.
You mention about an issue with OSRAM to me in this thread. After reading the link, the issue related to buffer overflow. A packet come out of overflow potentially will be an invalid packet (for example, crc can be wrong). At mac level, 802.15.4 has CRC filed in the frame to be check against. When it arrive at the environment sensor, this will be count as dropped packet. This is a possibility.