So my world is a world with a lot of running command blocks (and Structure blocks).
It worked before, but only after I exported it did it stop working.
(Whether or not the exporting had anything to do with it, i have no idea, but either way, it happened, and the next day the world wouldn't open)
note: i have copied the world before, but this is my first time exporting.
Also some context
I have been copying my Win 10 world to my iPad mini. I first did it by zipping a copied file and so on. Either way, I have a older save. This version was when I found the export button and tried it out.

After moving it to my ipad, I vaguely remember it opening properly (but just like the win10 version, it wont open later).

Also, remember how I said I had a lot of running command block (and structure blocks) ... I meant it. some Command blocks stopped working due to how many command blocks were running at that time. (whether that is a bug or a preventative measure, idk). I have no idea how many repeating command blocks were running at that time, but i think it is safe to say that there were atleast 8-10 (not as many to overcrowd the commands running at once, that was simply to show how many command blocks there were) phew... (a note, there were very minimal entities on the world. The world is flat. The structure blocks, while many, have remained fairly consistent for a while. With maybe 4-5 more than my older copy)

Attached is the world file. (I renamed it to "Spleef", though the real world name is "minigames")

tl;dr I have a world that has a ton of command blocks that may have been running when world was last closed. Now the world won't open.