Squat depth was good!
Your 275 pulls looked good too.

On the 300, I don’t know why it didn’t move.
It looks like you didn’t fully commit to it.
On the 275 you lifted it pretty soon, on the 300, you stayed at the bar for a bit and prepared mentally longer.

Best guess, you psyched yourself out as it was heavier.

When you are at a heavy pull, a lot of times people will pull and then stop because they think it won’t move, but a full commitment often make it move.

Think less.
Lift more.