That's an odd one Charles.

The only thing I could find was in the Errata sheet.
It says it's "Rare", so it's probably not it, but since you say it only happens on power-up, it might be worth a look.

8. Module: Reset

It has been observed that in certain Reset conditions,
including power-up, the first GOTO instruction
at address 0x0000 may not be executed. This
occurrence is rare and affects very few applications.

To determine if your system is affected, test a
statistically significant number of applications across
the operating temperature, voltage and frequency
ranges of the application. Affected systems will
repeatably fail normal testing. Systems not affected
will continue to not be affected over time.

Work around
Insert a NOP instruction at address 0x0000.

Date Codes that pertain to this issue:
All engineering and production devices.