The collision priority management of the MPC5500 family causes, that lower priority messages are canceled by higher priority messages if they occur at the same time. Refer to chip documentation.

All messages have the following priority: WPM - OTM - BTM - DTM. A BTM message which attempts to enter the queue at the same time as a watchpoint message or ownership trace message will be lost. An error message will be sent indicating the BTM was lost. The following direct/indirect branch will queue a direct/indirect branch w/ sync. message.
The count value within this message will reflect the number of sequential instructions executed after the last successful BTM Message was generated. This count will include the branch which did not generate a message due to the collision.
A DTM message which attempts to enter the queue at the same time as a watchpoint message or ownership trace message or branch trace message will be lost. A subsequent read/write will queue a data trace read/write w/ sync. message.