Cannot open .disc files

[Fender4]

Using Toast 18 Titanium on iMac OS  High Sierra (10.13.6).  All was well until the last Apple OS security update.  Since then the application cannot open the .disc files that it created.  Everything is fine all the way to burning a DVD, but once I save the .disc file and close the application, it crashes when I try to reopen it by any method (Menu: Open Recent, Open; Drag and drop; and Double click the file in the Finder).  Contacted customer support, who tried their best to help me out, but to no avail.  Sent a crash report to Apple (and we all know how well that works out, right?).  So now, I'm throwing it out for the community to see if anyone else has experienced this, and if so, what's the fix.  Stay well y'all.