Some quite similar requests fail but it's not clear why

[0x6e69636f]

By fail I mean : IF won't execute the command.
Some very similar requests fail but I can't understand why. It doesn't seem to be an encoding problem nor a question of length, see these examples :

• None of the examples provide the length of the data string.
• From the 7b byte, everything is similar.

This will fail (called with Java Socket class) :

0000   00 30 7b 22 43 6f 6d 6d 61 6e 64 22 3a 22 43 6f  .0{"Command":"Co
0010   6d 6d 61 6e 64 73 2e 46 6c 61 70 73 44 6f 77 6e  mmands.FlapsDown
0020   22 2c 22 50 61 72 61 6d 65 74 65 72 73 22 3a 5b  ","Parameters":[
0030   5d 7d                                            ]}

This will work (called with Javascript, with encoding through uint8Array etc):

0000   30 00 00 00 7b 22 43 6f 6d 6d 61 6e 64 22 3a 22  0...{"Command":"
0010   43 6f 6d 6d 61 6e 64 73 2e 46 6c 61 70 73 44 6f  Commands.FlapsDo
0020   77 6e 22 2c 22 50 61 72 61 6d 65 74 65 72 73 22  wn","Parameters"
0030   3a 5b 5d 7d                                      :[]}