Model cant detect objects when camera angles change

Hi all. For now i have been able to create custom model from my own dataset. Specifically i am working on custom model for detecting vehicles on the road.
Surprisingly it can detect vehicles very well as i expected, but when i try to test with different camera angles, model can not detects any objects, zero detection.

As far as i know, one reason this happened because my model "is not general enough" to detect to objects with different environment (angles, brightness, size) from dataset. And one way to cover this issue by having more dataset or by augmenting the dataset. Is my interpretation correct or am i missing something here?

Thanks in advance @EdjeElectronics , tutorial you made is lifesaver for me.