I was having a look at an old question of mine when I browsed the reopen review page from the timeline.
I scrolled downwards and realized the Review completed panel comes along for the ride. While that might be status-bydesign, tags flowing over top of it as pictured below probably isn't.
Here's a .gif of the Question and Duplicate tabs flowing over it as well. Note that the timeline button also flows over. If vote buttons are present, they will also flow over it.
Reproduced on Chrome and Microsoft Edge.
Update
Per this now-closed question by Tiago Martins Peres, this issue also happens in other Review types, namely Late Answers, First Posts and Low Quality Posts. In addition to that, it is causing the action buttons on reviews to become unclickable if you scroll low enough.
As a temporary workaround, you can use Samuel Liew's ReviewQueueHelper, which fixes this issue.
.js-review-bar { z-index: 999; }
to the CSS I use for my personal adjustments. There's probably a number which is more "appropriate" within thez-index
values which SE uses, but that worked for me.