I take it you mean slaves. The CAN bus as such doesn't have any master, unless you implement that in an application layer protocol. It is using bit arbitration with collision avoidance, so it is not possible for two nodes to send at the same time. If someone with higher priority sends, the CAN controller in the S12 will wait until the bus is available and try again. Lower CAN identifier means higher prio.
The bit rate will only cause problems if you are clocking the CPU (bus clock) with a frequency that can't be divided accurately enough, I believe CAN expects 0,5% accuracy. But since you can transmit and receive, that seems unlikely.
It sounds like the problem is caused by your program and/or hardware.
