Using 2 multiplexers to have 16 RFID working

Hi,

I've been working on a project to get 16 RFID working to do a Sudoku puzzle.  
 

These are the component that I'm using :
DFRobot 1-to-8 multiplexer (2 with addresses 0X70 and 0x71)

PN532 NFC RFID Wireless Module V3  (Link)

Arduino Nano

So far I can have 8 RFID working at the same time and both multiplexer are working when alone on the arduino
It seems I can get 16 initializing the RFID but when it's time to loop them to see if they have a new tag, it's not working on 90% of them.

I tried to select a port outside of the range 0-8 to make sure none of the port of the multiplexer were selected since they are both listening (both used the function .begin ).  
I did not found a method/function to put a multiplexer to sleep like I2CMultiplexer.stop() or I2CMultiplexer.pause() per example


Here is the code I'm using so far :   https://pastebin.com/UnGrmjv5


Thanks in advance