There appears to be a bug when decoding an empty 2D array using "JKI JSON Serialization.lvlib:Unflatten From JSON String.vi". When the variant that comes out of the Unflatten vi is passed into the Variant to Data vi, it causes an error 91 to be thrown. Looking at the variant produced, the problem appears to be in how the array dimensions are reported in the variant. The variant from the Unflatten From JSON String shows: "" where just taking an empty 2D array and converting it to variant shows: "[0x0]".
JSON 2D Array Error.vi