The Main Subject Looked Fine. The Chair Didn't.

The person looked fine.
The coffee cup was still on the table.
Then I watched the clip from Seedance 2.5 again and noticed the chair behind the person had moved.
Not across the room. Just far enough that I went back to the beginning to check.
It had definitely shifted.
I Wasn't Looking at the Chair
The first time through, I watched the person pick up the cup.
I checked the hand, the cup, and the movement between them. Those were the things I expected to go wrong, so that's where my attention went.
The chair barely registered.
Once I knew it had shifted, though, it was hard to ignore.

I Watched It Again Without Following the Person
On the next pass, I mostly ignored the person.
I watched the table, the chair, and the objects around them. There was nothing else dramatic hiding in the frame, but I noticed things differently when I wasn't trying to inspect everything at once.
Now I sometimes watch a clip once for the main action, then again with my eyes somewhere else in the frame.
I'm not looking for a perfectly frozen background. A curtain can move. Someone can pass behind the subject. Things can change when the scene gives them a reason to.
It's the unexplained changes that make me go back.
I Left Some Things Alone
If something shifts slightly near the edge of the frame and I only notice it after replaying the same few seconds several times, I may leave it alone.
The chair was different. It sat close enough to the person that the change became distracting once I saw it.
If the scene is meant to match a real product or place, I'm more careful. I check the details that actually need to be accurate against the original reference.
The person was fine.
I just hadn't been watching the chair.