When debugging with the variable values shown on each line in gradient gray background, the active (current) line that the program has stopped on, the breakpoint red dot and the yellow "current line" arrow are hidden (written over, or not displayed) sometimes.

Often while single stepping, the yellow arrow shows for a split second and disappears.

So if you are looking around in your code with the cursor on another line, there is no indication which line the program is stopped on. In older versions you could always see the current line arrow and the breakpoints, but now they are sometimes gone on the current (stopped on) line.

It is my guess that it has something to do with the feature of showing the values on the already executed lines of code.

Some debugging sessions seem to be worse than others, but that is only a hunch. But it seems to happen in every debugging session at least on some lines.