FX100 X-card pins not working as specified

We are trying to utilise the GPIO pins for the X-card slot, but not having success.
According to the documentation: Setting the GPIO as an input input
Enter the following commands:
AT+WIOM=1,“GPIO21”,0 -> this command activates GPIO21 as an input.

AT+WIOR=“GPIO21” -> this command reads the GPIO21 level and returns the value “1” which represents a HIGH level.
Pull the GPIO21 pin to GND, and read again. The return value should now be “0” which represents a LOW level.

This works for the GPIO19 and GPIO20 pins, but not the GPIO26 and GPIO27 pins
Above pins are listed in the Fastrack Xtend User Guide as valid GPIO pins so we do not understand why the 26/27 pins do not work.

Our engineer has been playing with the modem and entered a slightly wrong command with interesting results.
He was attempting to set a GPIO (3 in this case) as an input. He mistyped the command as:

AT+WIOM=2,”GPIO3”,0 the typo being ‘2’ in the middle of the command.

The modem then output a list of what appears to be all the GPIOs available. The format was:

…………… down to

The interesting part is that GPIO26 and 27 are not in the list.

Any help will be appreciated

I have gone through the customer guidelines and it is mentioned that these GPIO are reserved. Even i try to change the GPIO configuration and got CME error:501 which means GPIO cannot be reached by device layer (for example the GPIO is not currently allocated to the user).