I ran into this same issue. If you select all three partitions and then click 'Copy selected partitions' you will only be able to resize the last partition. If you select the first two partitions, click copy, resize the second, then select the third and click copy again, it will complain that there is not enough space. However, if you instead click and drag the partition, it works. I suspect the 'Copy selected partition' button is attempting to copy all three partitions, not simply adding the third partition.