Hello, when I rotate my camera orientation on mini 3 pro. There is this lag as the video shows. Is this normal ? It seeems like it didn't do it before the dji fly app update.
https://youtu.be/8Fagqhueli8 (video link)

Hi there. Thank you for reaching out and we're sorry for the trouble. Can you please try to perform the gimbal calibration and then check if the issue persists? Please keep us posted. Thank you.

Hm... Nice question.
I usually don't use the vertical camera mode, and my impression was that the lag you see is normal: It looks the same way on my drone, and on the videos I've seen on YouTube.
However, after experimenting a bit and repeatedly switching between vertical and horizontal mode, I've noticed that in some cases, the lag is as long as in your video, but in some rare cases, it's much shorter.

Perfectly normal, happens on my drone as well. Sometimes it's a bit faster sometimes a bit slower.