I think there are a few cards which we can use indefinately. And I'm not talking about those multi dmg dmg cards with infinite activations. I have a 'succubus queen' with 3 turns skip skill which only shows skill lv 1 in description, but not the number of activations. I am able to use its turn skip as much as i want with no disconnections. Then i have another atk up card 'parvati', lv 10 skill but no info on number of times it can be used. but, if i use it more than once, i go dc. So, there may be some cards that may have got bugged. I haven't tried with original apk, only with modded version.