Thanks Link; this issue was corrected by a new/reset all, then merging a new template file into the current project. It would be nice to know where these library parts reside however. I tried to trace location first by system name search, then from Drawing Settings Title > Load Other Drawing Title > Go to Library, & manually searched every folder possible. Finally tried to find the part using Find Library Part in the Object Tool DB. This issue is resolved, except for the mysterious location of these Title Type library parts.
AC25 v. 5005 w/ MEP, Cadimage, Twinmotion 2021 using AC from AC6.0, 2.7 GHz 12-Core Intel Xeon E5 (OS X 12.2.1 Monterey), AMD FirePro D700 6GB, SSD, Artlantis 2019, Adobe CC. Used AC on both platforms.