This is the method I was using to open the bag the second time the snap pulled out. I think it's pretty ridiculous anyway that you would have to use some special method to open the bag to avoid damage. There is a tab there. Pull the tab... bag opens. End of story.
Jim,
This was not done intentionally as a "special method". It is just the way I open the bag. Who knows why I do it that way.
Hopefully, you resolve the issues, and get a bag that works for you.
PS. We both had Vaude bags before the Ortliebs. The mounting worked well, but the bags were not waterproof, and needed a rain cover. They are still being used on our utility bikes, and are reasonably durable.