Hello everyone.
I have a Teensy 4.1 connected to an 4.2" oled and a few sensors. Among the sensors I want to connect to the SPI bus two MAX31855 thermocouples for measuring temperature.
I have designed a PCB on which all the parts fit. When I solder just one of the MAX31855 ICs everything works great. The temperature is read and displayed on the oled without any problems.
But when I solder both the MAX31855 ICs on the PCB, the SPI bus (I *think* it is the SPI) is having some weird issues. The oled begins to display glitches (random lines or dots on the screen, the data displayed begins to move around) and even sometimes the SPI bus stops working (the oled is all black and the SCK pin 13 on the Teensy stops blinking). I think the SPI bus is somehow affected because I also have a NRF24L01+ module connected to SPI and when the glitches appear the module stops working.

Here is what I tested so far:
-The glitches appear only when both the MAX31855 ICs are soldered on the PCB
-It is not a PCB issue. (Both the ICs work just fine when soldered just one at a time in either of the PCB footprints.)
-Both the CS pins of the MAX31855 ICs have separate pull-up resistors.
-Software is not the issue because the glitches appear even when the Teensy is coded just to turn on the oled and display something, without any code/library for the MAX31855 IC. And the temperature is shown correctly when only one of the ICs is soldered.

If you need to see the layout of the PCB you can find a copy of my project here.

Could anyone tell me why this happens? What could I do in order to be able to use both the MAX31855 ICs?

Thank you very much for your input.