Stu is correct, but to be more specific, the shim goes under the black piece in the photo. I originally made a silicone shim and put it under the larger metal piece. That was before I saw a shim and only read about it. It worked but still momentarily lost power on rare occasions. The Giant shim...
This is likely a bad connection between the battery female terminals and the male terminals under the battery. Giant has a small shim that goes under the male terminal block so that it increases the height of the block about 1mm. This makes the male ends go about 1mm deeper into the female ends...