SanDisk 4TB Extreme Portable SSD

I have used SanDisk products for years and have always been very happy with them. This 4TB External SSD just changed that. Maybe this is an isolated case, but this SSD behaves intermittently. It is of no value to me as a backup drive (which is why I purchased it). I am seeing failures of many types as I try to load my files onto it. I see write failures due to device being write protected (it's not); I see failures reported as hardware failures; there have been other types, as well; and sometimes whatever is going on just blows my Windows 11 OS away. When this began after a few hours of steady copying, I assumed there was possibly something awry with the unit's formatting. So, I reformatted it... a full reformat that took hours. (Though I must admit I'm not sure what improvement I expected from formatting an SSD). In any case, it didn't help. I started the return process through Amazon, but am not going to follow through. I realized that I have recorded some important data on the drive and the only way I feel sure I can "remove" that data reliably is to destroy the drive. So, I will not follow through with the return. I'll just be out almost $300. FYI, I had previously ordered a 4TB drive from another well-known vendor and have been using it for a couple of months. I ordered the SanDisk drive because I needed more 4TB units, the SanDisk unit appeared to be more robust, it had an appealing appearance, and I trusted the SanDisk name. I don't think it makes sense to suddenly shun the SanDisk name because of one incident like this, but I'm ordering a copy of the other brand to replace this costly disappointment. - - - - - - - - - - - Update: I did hang onto the drive and tried an experiment with it later. My failures occurred when I was using BeyondCompare4 to back up my data. I was copying about 2 TB from another USB drive to this one. Often when I am backing up this much data, I like to watch different chunks of data get backed up at the same time, so I often have 3 or so backup threads going at the same time. I have often wondered if this kind of thing might be more stressful on the drive, but I have been using BC for several decades and have always done this. When I did this with the drive I purchased to replace this failed unit, I saw a couple of mild failures on that drive as well. Those failures were just that the data didn't copy successfully. This was nothing like what I saw with the SanDisk. Since I have often wondered if "pummeling" a backup drive with multiple backup threads might be a problem, I just went with a single thread after that. It worked fine on the newer drive. So, what the heck... I tried it with the SanDisk drive as well. That worked, too. Hmm... Keep in mind that I have been doing this for decades and I have not seen this problem before these episodes. I also have been using another 4TB drive for 2-3 months and it has not failed. I now suspect that larger drives may be more vulnerable to this type of problem. Is it timing when being accessed by multiple threads? Is it heat? Or other? I did not notice either drive being hot, but I don't have a thermometer attached and, sorry, I'm not that interested in pursuing this to such a degree (no pun intended). I use multiple backup drives "all the time," so the failure of one is not a disaster for me. In the future I will resist the urge to run multiple backup threads at the same time. Will this make the drive reliable? I don't know. Maybe a year from now, I'll update this review again when I've had time to see if this matters. Meanwhile, if you are having trouble with this drive or any other, pay attention to "how hard you are using it." Maybe these things are just not as fit for handling heavy usage as smaller units are. So, maybe if you know its limitations, you can use it successfully.