Using 3.1.6252
On the first tags page when you select a field to edit and then switch to the next file using the arrow buttons, the cursor stays in the same field.
On Tags(2) when you select a field to edit and then switch to the next file, the cursor loses focus and you have to select the field again.
It keeps focus in 3.0.6230 (which I use as a portable version) so I'm guessing it changed somewhere in the 3.1 update?