The supposed thrust of the EmDrive is very small. But the device has a lot of wires with current that can be equivalent to an electromagnet, and very hot parts that can create air currents, and ...
If you have not done few physics labs, it's easy to underestimate the measurement problems and the level of noise in experiments.
Most of the Physics community thinks that this is an experimental error. One symptom is that at lunch in a Physics department nobody talks about this. If this were real it would be a groundbreaking result because it breaks some of the most fundamental Physics laws.
