I work on six NASA missions, including one that has been staring at the sun 24/7 for the past 7 years. nothing from this mission has seen anything like that. but more importantly and to the point where you say you dont understand how a data storage and someother (most likely flipped bits during transmission) could cause that. First of all, it is hard to understand how this would happen without understanding how the instrument that took the data works. Wiki didnt provide any useful information but my best guess would be that it is from SECCHI. i cant say for sure how they come to get their digital conversions but at some point before the data is stored/transmitted to earth, it is converted from analog to digital via an A to D converter. a simple 8 bit A to D converts an analog signal to an 8 bit number (0-255) based on the intensity of the analog signal. These bits are then stored, transmitted and most importantly interpreted. Based on its highly elliptical geocentric orbit and its downlink of 720 kbps, i would say the transmission is most likely done on either X, S, or Ka band. Ka band for instance, is absorbed by water which means that there the probability of transmission errors greatly increases when it is cloudy at the ground station. So lets ignore framing and parity and say that i am sending 0000 0000 but due to the cloud cover, the first bit gets flipped and what the ground station receives is actually 1000 0000. that means that 0 was sent but 128 was received. when these numbers are interpreted, clearly the final result is going to be inaccurate. that being said, STEREO most likely has complicated CRCs and other EDAC algorithms to prevent this, but now you should understand how storing a 1 instead of a 0 could be interpreted incorrectly and result in a reflective object.