Hi Vince, it's been awhile.
I've never encountered your specific error message while using RR, but I have encountered other situations in which RR/TSUtil failed to complete successfully because of errors (some reported, some just freeze ups). I do have some thoughts that might help.
From your description, and having had some experience myself dealing with RR/TSUtil errors with extra large routes including PRR-Eastern, I suspect sheer volume may be the culprit. Maybe there are too many of something that exceeded an upper limit inadvertently programmed by the programmer.
Here's an idea to see if this is the case, and if so, maybe there is a "get-around" that might work. Move a bunch of ".s/.sd" files out of the previous version of the route into a separate folder elsewhere to reduce the volume being handled, then try the function again. Perhaps everything else is/was properly handled except for the processing of the Shape/Texture folders of the two routes. By reducing the volume an EOJ might occur with output files and no "76" message.
Of course, the new execution might detect missing Shapes and quit for that reason.
If that doesn't occur but the same "76" message does after reducing the volume of Shapes, then maybe that isn't the culprit afterall.
Or maybe the new execution might get beyond that and produce output files as if normal completion. That would be progress. If so, the next step would be to apply the patch and see if the route will load.
Of course the the patched route may fail to load.
However there is a better possible outcome. The patched route might load and appear to be okay except for detection of missing Shapes when navigating to affected world files. There may be a way around this if you get this far.
Anyway, I hope this helps. I'm curious about results if you try the above, and about your plans if all else fails.
Chuck R.
"More railroads crossed each other more times in Chicago than anywhere else in America"
Jon R. Roma, Trains Magazine, July 2003.