What effect does Gamma radiation sterilisation have on embedded electronics devices
The prognosis is probably not too flash [groan].
Depending on energy of radiation, device death ranges from possible to essentially certain.
You can potentially expect all the effects you described.
Even if apparently still operating you may get increased leakage currents and 'general unhappiness'.
What was the gamma source? what energy?, what distance? Why?

Radiation Damage in Electronic Memory Devices PDF
HTML
Says:

...  Obtained results show that gamma radiation causes decrease in threshold voltage, being proportional to the absorbed dose of radiation.
EPROM &amp; EEPROM: ... Gamma radiation causes generation of electron-hole pairs in SiO2 insulator of the gate. The number of generated pairs is directly proportional to the energy deposited in material, depending on the total absorbed dose of radiation [8, 14].  ...
Conclusion
... Based on analysis of data gathered from performed experiments, the exposure of semiconductor memories to gamma radiation causes three effects: holes being captured in trapping sites of an oxide, injection of holes from oxide into FG, and emission of electrons through FG-oxide interface.
The generation of electron-hole pairs leads to trapping of positive-charged carriers (holes) in insulator, causing negative shift in  characteristics. Namely, positive-charged carriers induced by gamma radiation require the increase of negative gate voltage to compensate the positive charge. It means that gamma radiation causes decrease in threshold voltage, being proportional to the absorbed dose of radiation.

NASA - Chips in space