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This limit is primarily around the basis of the resman (resource manager) in the toolset and game. The game tends to load bigger ones fine, but the may load the module but things may not be fully loaded into the game (scripts may not fire, placeables may not appear). The toolset resman may lose resources (meaning things start to break, but it's unknown what rhyme or reason there is to it there).
Notably the toolset does not warn you of this limit when saving or opening!
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