to exploit this bug, what I did was quite accidental. I simply completed all 20 of the weekly normal quests for week 1 upon starting the game, which had already been in progress for a couple of days, but I managed it. You then get to claim one (1) "Normal chest" which drops cash, gold (slightly more premium currency) and boosts at random.
I noticed after I collected it, then changed menu, then came back, the chest could be claimed again. Repeating allows this to happen indefnately. :D
I now have infinite ammo (never need to buy more), no reloads (never need to reload the gun either), and unbreakable weapons (never need to repair). if I feel like it I can also double cash gains from missions.
For free.