When I look up that incubator online they say it is a forced air, which means it has a fan in it to keep the temperature the same throughout the incubator. It is not doing that if your measurements are right.
Have you heard from them how to adjust the humidity? For them to not include that information does not feel right.
If it were me and I had all this, I would return that incubator if you can and try another make and model. I just don't get the feeling they know much about incubating eggs.
38 C = 100.4 F
35.8 C = 96.44 F
2.2 C or 4 F difference in various places inside is unacceptable in a forced air incubator.