I agree with you that it is randomness but not 50% keys for 50% cases .

the percentage differs according to some factors and from what I experienced it elevates for keys when you save some

I think what EvilAngel is saying is ultimately, your sample size is 1. What you are perceiving to be a pattern is actually just the randomness of the system. Unless you have over 1000 of a key, the drop rate of keys to boxes is random. I'm sure it has some predetermined ratio, (let's assume 4:1 which are COMPLETELY made up numbers)

4:1 means 80% chance box, 20% key. Even with those odds, you can still get runs of keys instead of boxes. Statistics says it's not likely, but PPS seems to exist in a world where statistical theory doesn't matter. The devs SWEAR that everything is random and there aren't any other behind the scenes factors that influence the streaks of whatever you happen to get a streak of (be it keys, or triple EXP, or triple Pero or anything else).

The Random Number Generator sometimes just likes a certain 'range.' and for no good reason, you get streaks of things. Still random, but it totally looks like a pattern to the casual observer. Hell, I would SWEAR there's some internal modulator that makes streaks of shit happen, but I get called a conspiracy theorist for that and Nutaku swears it ain't so.

So assuming Nutaku isn't lying, it's all just random chance.

Well, i'm kinda economic, so i open my Silver cases only when i need an SR girl card to complete a "Get 1 SR" Daily Mission, and always keep my silver keys for when i'm out of Silver Cases that my friends have opened for me, or when i see that a silver case found by some of my low-level friends, or those of my friends, who frequently open my own glod and silver cases (or just a person that i fell like to help to not lose their silver case), so my silver keys amount is almost always is around 20. I don't know if it is my luck (bad luck?), just a glitch in the random pattern or something to do with the current PeroGambit, or is it even the way it should be, but i'm getting alot more of silver cases this time, rather than silver keys.