The guild chest and all chance events are random. The only question is when the random roll occurs (typically before a shuffle), but there's not some guy in a dark room deciding these things.
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It's randomly chosen the first time you unlock the chest, at least that's what I can tell. The roll doesn't re-occur once there's already been a roll, perhaps to save server CPU cycles. I'm guessing the choice to do this sort of thing was made as a way to save hardware costs.
The labyrinth tiles seem to be set when you start the labyrinth run. When I got disconnected the other day, I was a couple of moves back from where I was when I got disconnected. I moved onto the exact same tiles and got the exact same results. It's not the first time its happened to me and it will probably not be the last.
Lab rewards :
If Token present, Far right. EVERYTIME!
Gems, Far left~usually, at least when I pick it. When both are present and I go for Token, gems sits middle.
Placement of the items are different for most of us. My tokens are generally in the middle and gems are one to the right.
Plus, the guild chest isn't so bad that it should just give you an item when you Claim from guild. I find that when I know I'm getting a map piece, I wait to use the map I claimed, then once am done sailing, collect my map piece from the chest. Also, opening and closing chests allow you to determine which jewel type you want, when in fact you know you're getting a jewel. I think the items in game that are predetermined aren't so bad. When the game wants me to have it, it will give it to me. This applies to everyone playing, so it's not like some are getting an unfair advantage over others.