Random red lines

The app appears good but there are several random red lines the app produces where there's not any text either. The display gets inconvenient to use.

Start by reproducing the display problem described in the issue and compare the result with the attached screenshot. Trace the rendering path responsible for red lines appearing without text; done means the app no longer shows stray red lines while preserving expected text highlighting.

Written by the indexing model from the issue text.