Tempo Track Graphical Problem

Hello! I’ve got a project (currently in Dorico 6.0.22) which is not displaying the tempo track properly. I can use the draw tool to add points which show up as signposts in the music, but I can’t see the line, which makes it pretty difficult to edit properly.

I opened up a new project and it doesn’t have this issue, so I’m worried that the file may have been corrupted? Thanks for the help!