I did not go into any folder. The CDP is saved into a folder on a a USB solid state disk. Tried clicking everywhere, with nothing to loose because I had a CDP backup, hoping for that magic click. While I am presented an option to save when leaving the Surveyor, the depository is the very area that was corrupted. I have had other errors in the long past where reloading the program showed that the "backed up" data was corrupted. I may be unusual but I prefer to be totally removed from any code in the program other that the Content Manager. The Export to CDP is the safest backup for my purposes.
The route is a creation of MGSAPPER. I have been messing with it through several iterations of Trainz/Tane/TS19. By now it is likely that most of it is changed in some way.
Given I am the only one with an event such as this I am going to point toward the computer. Having some knowledge of how the darn things work, some fairly simple things can become very nasty and hide within their intermittent nature. If you listen to a radio you can actually hear noise. That same kind of stuff is in your PC case but at a stronger level. If a component gets a little off specification and lets some noise into the wrong place - corrupted data. It either crashes the computer, or shows up later as a corrupted instruction for the computer to stumble across and do something very stupid. The user may see weird problems only once every 2 years or every 2 hours. You will never find the primary problem. In the case of the poor little PC that ain't gonna happen it may outlive its owner.. In a larger data center they do the analysis and pop out the suspect board with the possible issue and scrap it. If that doesn't fix it they scrap another board.
Could this have happened in my case? Something told the program to not store/save elevation data except for the active section. Chasing a one-off, is a waste of time/money. It might occur again and hopefully the victim will have a memory of preceding events superior to mine. These problems are much like the "cold case" TV programs. Somebody takes the program listing (cold case file) home every night and searches for a programmatic reason - volunteers?.
As a further aside I worked an intermittent problem once that caused payroll for several manufacturing plants to be rerun and pay to be delayed. The union was making nasty threats. With a trusty oscilloscope and a listing of the program instructions several areas of the computer were checked. Finally one check showed that the computer was looking for one of those tiny data pulses at a specific time. Most of the time it found it, but computers are impatient so it only looked for a few microseconds and temperature could change conditions. Leaving a door open behind a specific area made it worse. The solution was to change the computer hardware so the pulse was looked for in the middle of the "look time" and not, as I discovered, on the very edge of the time slot. Your home PC could have the same problem. Good Luck.... I was almost fired for making a change to the customer's computer without going thru proper channels.