Is the summer event part 2 bug?

My character keeps rolling back after finishing the (Shadow Grotto) dungeon, but consumed energy. Items disappear and achievement resets 

http://onigiri.cyberstep.com/_/forum/
http://onigiri.cyberstep.com/_/forum/viewtopic.php?f=10&t=13357
Srayer wrote:My character keeps rolling back after finishing the (Shadow Grotto) dungeon, but consumed energy. Items disappear and achievement resets