Volume Region

I have just purchased the 2019 version and successfully created the surfaces. Often time, we need to know the cut and fill for many regions in a project because they all have different production.
However, I have problem creating volume regions. I created the first volume region with no problem. However, when I start adding new region beside the region, I always get an error "validation of breakdown fail" or something like intersection end. I tried snapping to the adjacent region or leaving a gap between the boundary, the same error show up. I was successful last week that a second region was created without touching the boundary of the adjacent region; however, when I open up the project again today, the validation error was displayed. I have spent hours trying to figure this out but with no success. Please provide your advise, thank you.