PotentiallyDropped if no fixesjust like other Tower defense mobage but this Bug Defenders with full of bugs,unfairly spike difficulty after Chapter 2, Highly insane Rank Up level up but abysmal to lower power level in units, even you grind; Highly difficulty in Heroes Materials farming; Skip System cant level your units as well; Over heating issues even in low settings (even used a gaming phone); Gacha Rate is a lie (total of 100 rolls only 4 SSR obtained); Overly Price materials in Black Market and most of all; Initial SSR units are not OP and doesnt create a potential META. (its better to get a SR assault unit crossbow user and its carries you all the way because of high damage and aspd.
I do suggest to try other games like; Counter Side, Millennium War Aigis, Arknights or other Good Tower Defense genre that doesn't gives you unsatisfactory. I mean if a Mobage game contents doesn't give you satisfactory, why bother to play and grind? its a waste of time.