Figured it out. Our model is actually hybrid 1D/2D, and these messages actually were for 1D CROSS SECTIONS (not 2D cells). Doh! Our 1D cross section River Station IDs represent cumulative feet which gives them a name that looks like a cell number. And our reach and river naming was such that it appeared the message applied to a 2D cell. So, the problem posed in the post wasn’t actually an issue at all, just took a closer look to see it.