there |ðe(ə)r| in, at, or to that place or position
their |ðe(ə)r| belonging to or associated with the people or things previously mentioned or easily identified
they’re |ðe(ə)r| a contraction of they are.
I see these words being used interchangeably here quite a bit and they truly shouldn’t be as they have completely different meanings. A sentence like; “I really prefer the Arctic Circle over a Genesis because there just a lot smoother and have a longer spin time. They’re bearings are a lot better too. Would you like to try my Arctic Circle, it’s over their.” becomes quite a challenge to decipher.