I know this is concerning a 7290 on a 8300 thread, but the issue is the same and I can't find any other discussion about it so here it is:
I have the same issue. I installed a game, then went on pocketmac to uninstall, and it wont uninstall. I have screenshots, and if i go under log, I see it is "unable to remove app: 2" and then "Status: 4"
Some have suggested going into advanced > applications > modules (then you see the app and library files, but no option to delete either :(