I have an old application which started from VDF6 and was ported through other migrations in time, now to VDF19.1 and running under Windows 10.
After the last couple of months when I thought the application was compiling and running correctly, I discovered that while it does run, at some point in time, the application shuts down without any message.
This happens randomly, at times after a couple of minutes of use (navigating and 'playing' around with different views), at other times, it shuts down just at the initial login screen (first screen appearing before the entire application appears) even if nothing is clicked and keyboard is not used. It just shuts down randomly.

The problem is that without any kind of message, I don't even know what to start looking for and that is the scary part.

To give some additional info in case it may help, there is some old, basic sub classing that was made back in VDF6 and these custom classes are still in use.
However, they never seem to have caused any problems, not even with the 1st attempts with VDF19.1 where most of the functionality was tested and worked as expected, and the app didn't shut down.
Since then, very few has changed, nothing at least that would raise a red flag.
Additionally, the application uses Codejock classes and the ribbon bar along with and older FCP.DLL which provided some functionality back then, and another DLL that communicates with a fiscal printer (taxation purposes) for the invoicing system.

I don't know if this is something that anybody has faced, I really hope someone can give me some feedback or ideas as to why this happens, helping me narrow down the possible sources of this darned problem.

Thank you