When editing a sumation formula, cell highlights disappear when I type in the input line of the formula bar. Is this normal?

When I first click in the input line of the formula bar, the cells in the summation are highlighted. Then, when I click in the input line of the formula bar, cells that were highlighted are no longer are highlighted. This makes it difficult to add new cells safely in the formula when you cannot see which ones are already include via the highlighting. Bug or normal? Is there a fix?

The normal thing was always like this.