Let me just say the new UI looks great, nice and easy to understand and easy to figure out, at first i thought there was nothing to improve. But leave it to me to break it.
While searching for replays if you hit enter key on the keyboard instead of the "search" button the search goes idle as following:

And after hitting "Back to all replays" the UI becomes blank:

But this is easily fixed by exiting and going back. Using the search function with the "search" button didn't have any problems.

The second thing i tried to break was the tag. By clicking the "+" symbol in the right window "Tags: None (+)". By pressing the enter key on the keyboard you can add lines as such:

Entering 2 lines resulted in a "ddd..." tag at first, but after exiting the replay menu and coming back, there were 2 tags, 1 for each line (i didn't take a screenshot of this one). To test how much i could add at once i typed in 5-8 lines and the screen was as follows:

After pressing "To Menu" and trying to go back to the replays the UI was dead:

I could not access any replays. Restarting the game didn't work. Deleting the replay also didn't work.