Why I can not see the system heap?

Hi, I am using tracealyzer with MPLAB and a PIC32 microcontroller in snapshot mode, when I run the program for 5-10 seconds and save the trace I can see the system heap:

but if the program keeps running for more than 10 seconds then no system heap graph is shown, why?

As this is a Percepio tool built into a Microchip tool - I would recommend posting your question to either Percepio or Microchip.