Upgraded Project Breaks Matchline Labels when Plotted from SSM

So we have an older project, which was last working perfectly in Civil3D 2018. We have many sheets along an alignment created using a referenced view frame group from the design file. We have all our sheets organized in the SSM. Our matchlines have labels like "MATCHLINE 121+50 (SEE SHEET 13-01)" After upgrading the whole project to Civil3D 2021, the files open fine, if you refresh everything seems fine. It is when you try and plot a sheet or sheets (to PDF btw) that the SEE SHEET part loses the neighboring sheet numbers and becomes (SEE SHEET ####). Now in all my many years of experience I've seen this happen before, usually something of a lost link or file moved or reference template renamed etc. But this time I can't seem to fix it so far. Any clues or ideas? Maybe an obscure variable I am missing?

Another thing that is odd, the newest linework added in that file shows through the wipeout borders beyond the matchlines... so something is definitely NOT working correctly... any help would be appreciated!