I just RMA’d my SanDisk 128GB a month ago because it would drop-out after about 3 or 4 GB into a file transfer. It only did this when plugged into a USB 3.0, which led me to conclude that it was an overheating issue caused by the higher performance of the drive when plugged into a USB 3.0 port. I could copy over 60GB in one go over USB 2.0 however.
Anyway, got my RMA back the other day. Same issue unfortunately. I got a great deal on this drive though (only paid like $15), but if I paid any more I think I’d be asking for a subsitution from SanDisk, i.e. one of their other equal or greater performing 128GB drives.
Definately a lemon this series of Ultra Fits. My last 64GB version had all sorts of issues as well, which SanDisk replaced with 2x 32GB sticks. No technical issues with the 32GB stick, but the keychain holder did break on one of them; yet another design flaw of the Ultra Fit.