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"Katzenjammer;c-2059620" wrote:
I dropped 500 overnight and asked why that would happen. I really don't care the reason,

Apparently you do care otherwise you wouldn't have asked.

"Katzenjammer;c-2059620" wrote:

it took all I had to stay 300-500 daily

And there is the core problem. If you are only just managing to maintain your position you are vulnerable to a variety of changing conditions in your shard.
* local meta shifts, even localized to a particular prize tier in a specific shard
* increased activity from people chasing GAC feats
* higher activity around the boundaries of prize tiers
* failure to invest in your team's gear/zetas/mods for an extended period
All of these things can lead to you getting dislodged from your usual rank range and once that happens you can drop a lot furher than you might expect.