The device is not able to mount only one card at the same time

I had stayed at the sister device to this reader, which has two hidden and again has two protruding slots, tested and sent back, and I have the same problem found with this unit, which has only two slots: Although two cards (SD and a microSD) can accommodate the device at the same time if you connect the Reader to your computer, only one of the two cards mounted, making it unusable for me, unfortunately, I will just have two slots so, so I do not always have the cards purity and need to get out fumble, but the reader can use as a USB flash drive. Moreover, it is always nice if you can copy from one card to the other, which is also not possible.
The reading and writing speed is slightly faster than my USB 2.0 Reader in fact, but the difference is not so spectacular, so Pi formatted times thumb twice as fast at a exFAT 256GB SDXC card, and an MS-DOS formatted 128GB μSD. The cap on the card is also a bit thin, who as already noticed other tests, but I see less than a problem, you can certainly make sparing use of the device, eventually breaking times each plastic, but now I do not see, as a major risk would be with this device.
For me not useful because of the Mount problem, so unfortunately goes back.