Sure, it could be that. But it could also be:
- A cleaning person plugging a vacuum cleaner into the power strip on the rack instead of into the wall outlet that's on an external circuit (combined with improper power filtering in the equipment).
- Electrical noise caused by some other crappy piece of equipment in the rack (combined with improper power filtering in the equipment).
- Errors caused by higher operating temperature.
- Errors caused by emissions from natural Uranium or other radioactive elements in the soil.
- A software bug.
- A hardware bug.
And if it happens disproportionately on one class of equipment, unless there are material differences in the amount of shielding, any one of those five is probably much more likely than cosmic rays, IMO.