I was having trouble getting 1 of the 8 hidden nuts in the arms to engage, one of the 4 that is completely obscured.
Out of curiosity I tried one of the m3x16 screws and it successfully engaged but was too long for the available space.
I was reluctant to try dismantling the sub-assembly because of the thread locked screws in the motor so I ordered some m3x14 screws and it worked perfectly.