I've been seeing reports of shutdown crashes resulting in the app loading with a "hole" in the map that won't correct itself. We haven't reproduced this here, so I'd much appreciate some information. It's a bit technical, but if you can manage it we'd be much more able to address this issue:
1) Is there still a map tile at the bottom of that hole? Rotating the camera to look straight down or switching to 2D view should reveal a flat tile below your others if that's the case.
2) When you use Finder to browse to /Users/USERNAME/Library/Caches/com.garmin.BaseCamp/TileCache/ and sort by "Size", do any of your tiles have a size < 2 MB? If so, please zip them up and attach them in a reply so we can start exploring how to avoid loading these tiles in the future.
3) if and only if you don't find any suspicious (< 2MB) tiles like this, does deleting the /TileCache/ folder before starting BaseCamp fix your issue?