Crashing ESP32 - Serial debug messages

I have an odd issue where the code on my ESP32 seems to run fine for a short period of time then I see this continually appear in the terminal window:

st:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
invalid header: 0xffffffff
invalid header: 0xffffffff
invalid header: 0xffffffff
invalid header: 0xffffffff
invalid header: 0xffffffff
invalid header: 0xffffffff
invalid header: 0xffffffff
invalid header: 0xffffffff
ets Jul 29 2019 12:21:46

Anyone seen this or could shed light on what is happening?

Andy

May have figured it out - I am using a Task and once I put a call to delay within the task loop, the error is not longer occurring. Does delay kick the watchdog?

Andy