Hello @C_Zuercher_APR ,
First of all, which version of our toolbox are you using? Is it MPC57xx 3.2.0?
I will try to guide you through what I've seen in the generated code.
First, there is an issue with how Simulink generates the code. As you see in the below image, for all 5 Message Tx Subsystems, Simulink generates a single function in which it will send only the 0x101 message-Id.

To solve this, you have to right-click on every Message Tx subsystem, select Block Parameters (Subsystem), go to Code Generation, and for the Function packaging select Nonereusable function

This will generate a function for each send block with the right message Ids.
Now, the second thing I see here is related to the FCAN_Receive block. This has to be called only once at the initialization and then retriggered every time in the interrupt to "rearm" the receiver. Now, basically you "arm" the receiver every 0.002s, in the step function. You can have a look inside the flexcan_slave_mpc574x example.
Also, make sure that if everything works, you have enough time to send all the 5 messages in the 0.002s.
Please give this a try and see if something has been changed.
Hope this helps,
Marius