Basically, the game just freezes on the black screen as you enter a secret base. I noticed it on the emerald 650 patch initially so I checked out mamama's base because I knew it was based off that one. I tested it on an existing save and on an existing base, on an old save but creating a new base and on a clean save and it's the same every time. The game lets you create a new secret base and close the text, however, as soon as you enter the base, the game freezes (Likely something was over-written which shouldn't have been). Contests are something that someone else mentioned but I haven't tested it myself, could possibly be caused by the same issue, but that's beyond my knowledge. Hope that helps.