The Reset App Bugs are a series of computing errors in Final Fantasy Brave Exvius which occur when soft resetting or crashing the game, resulting in its closure and eventually when the player reopens it. These are the known lists of known occurrences, some of which have been fixed as of later updates. It is to be noted that it is not fully known whether these were indeed unintended bugs, deliberate or just a side-effect let slide but fixed due to balancing concerns, they are as follows:
Turn Count Reset
The error caused turn counts for predetermined patterns to reset. Given several Bosses rely on turn counts to apply certain attacks (i.e. some performed once every 3 turns or once every 4 turns), this error effectively made it so those attacks could never be used as all the player had to do was soft reset the app and in turn the Boss' turn count would be reset as well.
It is interesting to note that in the Global version of the game an update was added which included a turn count for the battle, found in the upper right section of the screen. While the Boss' turn count was reset, the "battle's turn count" did not. This result in rather strange phenomena in which Bosses would behave like if it was the first turn while in truth it could be the 10th or 20th turn.
Because the Battle Turn Count was unaffected, some turn based consequences were unaltered, for example, some Bosses stopped dropping Limit Burst Crysts after a certain amount of turns, which remained true no matter how many times the player resetted the app.
The most famous examples of both were found in The Rumble of Malboro Trial, where many players exploited the Reset App to avoid the terrifyingly perilous attacks like Devour, Berserk Touch, Tentacles Blow and Tentacles Rampage. The lesser Malboros would stop dropping crysts after 20 turns of being summoned, but would start dropping them if resummoned again which reseted their counter.
This problem has been fixed.
Attack Turnout
Most famously known as the RNG Bug or similar terms by fans, this programing error caused certain outcomes to change depending on the attacks involved. At its most basic, this error caused (if used during enemy party turn), to change the target of their attacks. Players could use this exploit in order to avoid certain units from being killed and having the damage (mostly from single target attacks) to be spread more evenly and ensure favourable outcomes.
There were some outcomes based on luck that were affected, for example if in a certain turn or threshold a Boss attack made it to choose between attacks A, B or C, the player could soft reset the app in order to have the Boss use the attack that better suited it.
Interestingly enough there are certain luck based abilities that were unaffected. Most notably are Setzer's Fixed Damage abilities which rely on luck. However the damage they will deal per turn is predetermined, so no matter how much the player soft reseted the app, the result would never change, the same applied to all turns.
It is also worth mentioning that soft resetting the app is a common technique when a player screws up a turn, a chain or some other move. Doing so during the player's turn will reset the players' turn as if starting it.
The most famous uses of this bug were during the Wicked Moon and The Fallen Ice Bird Trials. In the former, the Boss Bloody Moon has a threshold attack whose outcomes is luck based from a checklist in priority order, and players could soft reset the app to get the least dangerous result. For the latter, the case is rather more infamous as the Trial is infamously known as the "Soft Reset Trial" largely because of a nasty preemptive strike that is potentially deadly for the player's units. As a result, players soft reseted to survive this attack on the best conditions and subsequently defeat the Boss.
This bug has fixed, so no matter how much the player soft resets the app, the results that happen in a turn won't change. The player can nonetheless, still soft reset the app if they committed a mistake they wished to fix during their turn.
Continue Bug
A more recent form of the Bug which has both beneficial and potentially imperilous effects. When the player soft resets the app (reportedly 2 times) during a battle (although it can happen in less than that), the player's units will appear as if the player used Lapis to continue from a Game Over, namely they will be with full HP/MP, have their Limit Burst gauges filled, the Esper Gauge filled, status ailments/buffs/debuffs removed, etc.
The game doesn't treat this as a Continue so the player won't fail missions related to no continues. The player also doesn't lose any mission achieved (i.e. if a mission demands using Magic Damage 3 times, and this condition was fulfilled, it remains fulfilled). Whatever HP the enemies have remains.
There are some problematic effects that happen nonetheless, for example, characters with build up damage, like users of Ja-tier spells, will find their stacks gone, so if they had built damage, they must start from scratch in piling their power up. If the player switches devices when this occurs it can happen that the battle is forfeited. Setup abilities (those that unlock other abilities) are also reset.
Some effects are not fully clear, like an enemy's buffs, debuffs, or other unexplored effects. As reported above it is not known whether this is intentional or not, as so far this exploit remains unpatched.