random deck changing bug

i was using kaiba as main character to level him up, dueled with SDs using my standard deck. then i built and tested a new LD farming deck using joey. after that, i switched back to kaiba and dueled with SDs. To my surprise, the set deck was changed to another kaiba's deck (not the standard one). while i switched again to joey, his set deck also changed (not the new farming deck i have used before). then, i changed again to another character one by one, their set deck just changing randomly. i didn't change the set deck between character switch (except when i built that farming deck). anyone have this problem too ?