I just did the one repair, and managed to recover from one error (a problem with the gold Kapton insulating film on the LCD, I think). I didn’t encounter your problem. Check all the ribbon cable connections and scrutinize your mechanical alignments around the ABXY pad.

And remember to take a break. Maybe sleep on it. We’re all better after we have had some rest. Sorry I can’t help more.

Thank-you.

I’ve got a flippi V8 and just on a whim decided to save myself some time for tearing it down.

The re-attachment of that first cable was a challenge, trying to wrestle the chassis, motherboard, and ribbon cable. I've written a short guide that makes it much easier, accessible here:

Re-installing the motherboard of the 3DS XL

During re-assemblhy, note that the peg between the joystick mechanism and the circle pad is rectangular, and must fit into the matching rectangular socket on the circle pad.

In my 3DXL, there was no IR board: the parts were installed directly on the motherboard.

I was completely successful, although it was rather harder than indicated. Took me about 2 hours.

The battery replacement is different than illustrated if you buy the iPhone 5s battery replacement kit from iFixit: If I bought a repair kit, I'd very much like to see it illustrated exactly. There is a good way to install the battery replacement kit that does not appear to be documented, which guarantees proper placement of the battery such that the power connector is in the right place. It would also be good to have a little more guidance up-front for treatment of the battery cable. It takes a little careful folding, and there's also a little routing of the antenna cable that needs mentioning.

The touch id cable bracket reattachment is a little glossed over. There are two tiny tabs on the socket that fit into two tiny holes in the bracket, and then you just snap it down the tabs and holes acting as hinges.